I rewatched LBT 11 today and tried to pin down as much stuff as I could. I hope this helps solidify, build, or eradicate your views on LBT 11 in some way.
Here’s a short summary on some of the parts: Some people probably dislike LBT 11 because Littlefoot lied; that the theme of LBT 11 was lying and telling the truth; and that some cartoony or childish elements, like anthropomorphized villains, unintelligent grown-up extras, and purer-hued colors in some places, existed. Still, there are many reasons to like LBT 11, such as the new characters, the relationships between Tria, Topsy and Cera, the radical theme of fibbing, and the humor and fun. Also, one can come to appreciate LBT 11 more by understanding WHY one likes or dislikes it in the first place.
My Proposed Reasons why someone might dislike LBT 11:1. Littlefoot’s voice actor had been replaced yet again after LBT 10, and this time with a quite different voice actor (Not that Thomas Dekker would have been the ultimate best choice; although I liked Thomas Dekker’s voice in 7-8, it sounded a little high or something in 9; nice, but not the most preferable, but definitely preferably over the guy who did the voice in 11).
2. LBT 11 contains the first and only song to my knowledge where more than one parent (or even adult) sang in a song (Mr. Thicknose and the Rainbowfaces I don't think were parents, and Pterano was a loner)
3. The tinysauruses are voiced by ëcartoony’ voices that are possibly more akin to other franchises. Either way, their voices and laughter are supposed to fit their cuteness and size. One does not simply make a bunch of ugly, deep-voiced, tiny longnecks.
4. “Creepy Crawlies” and “Creepy Crawlies Reprise” are too close by each other in timing.
5. The parents were more often than not made to look silly (though this isn’t abnormal for the LBT series; in here they’re made to be goofy rather than the usual argumentative)
6. The fact the tinysauruses tried to hide from Big Daddy when Littlefoot first meets the tinysauruses.
7. The fact that Mr. Threehorn believed the tinysauruses ate all the leaves off the bush Littlefoot had took from.
8. This point is both part of this list and the next: The gang have lied and run away before, LBT 2, 7, 8, and 9 as some examples for stretching the truth. Still, for Littlefoot to do that is quite unlike him. If he had shown more shame and not lied multiple times, it might have seemed more reasonable, but then the plot wouldn’t have really ëbuilt up the blame’ as much. Even with that said, his integrity was pretty low on this film, because he lied to everyone in the beginning, then to the tinysauruses, then ëhalfly’ to Big Daddy, then he tricked his friends to go somewhere else to save two of the tinysauruses from being found. Just remember that not telling their parents where they were going in all the previous films was still the same as lying, EVEN if for a good cause. Then again, on LBT 11, the rest of the gang was being secretive when trying to find out what Littlefoot was doing. In the end, Littlefoot was very sad about what he had done. Just because lying is a common theme in other media, doesn’t mean the moral was ëcookie-cutter’; most of the early LBT sequels had a mix of morals that weren’t really defined (the gang mainly went on fun adventures, helped others and each other along the way, and sometimes learned their lessons for things they had done, but usually because they had ran away, rather than something else). In summary, lying is always a touchy subject because words can be a very damaging thing; running away to help someone doesn’t click as much as being very damaging compared to tongue-related or emotional problems. At least that’s how I see it. In the end, I can understand why people might dislike the movie for this. Lying hadn’t been discussed or a too common thing in LBT, and so making it the central part of the story, and having Littlefoot of all the perpetrator might have been too much for some people; still, as a person gets older, they become exposed to all kinds of things and are more likely to commit a new harmful act than before, and that’s just a fact of growing-up really.
9. The adults make typical hollers and angry motions to agree with Mr. Threehorn. In previous films, they would usually argue with each other instead, with more real dialog, and less pure anger.
10. Also, the adults are so quick to exterminate or deprive of sustenance the tinysauruses. Though in hindsight, none of them knew how the tinysauruses looked like except Topsy and Tria, and they did eat all the tree-sweats that had been likely ripening for almost a whole year.
11. The raptors are somewhat less intelligent than sharpteeth usually are (I think? Hahah); and the raptors did look a little more cartoony. Oh, and they laughed.
12. The fact that the raptors heard Big Daddy from super far away.
13. The colors of SOME of the extras had quite varied colorings than what a viewer might be used to (even for LBT 10).
14. If you’re looking closely enough, seeing all the extra dinosaurs as 3D at the end of LBT 11 might be anti-climatic.
My Proposed Reasons why someone might dislike LBT 11, but could possibly be disliking it for the wrong reason; though some may be argued:1. The tinysauruses, simply for being tinysauruses.
2. Tria being pink.
3. The sweet-tree’s flowers are pink.
4. Some of the lineart may be a little thicker than normal, but one could say the same about Charles Grosvenor’s early LBTs too.
5. Cera easily upsetting Littlefoot in the beginning (this was a very reasonable scene. Cera was made to look bad and so she took payback. Also, the remarks she made about Littlefoot and how Littlefoot reacted are very similar to LBT 1). Still, it was sudden.
6. It’s understandable that Mr. Threehorn would desire a wife again since his previous one had most suredly passed away (Cera’s parents had both reached the Great Valley to my knowledge).
7. The members of the gang of five have stretched the truth before: LBT 2, LBT 7, and LBT 8 off the top of my head. It’s just that LBT 11 kind of including too much lying if you ask me.
8. The ëmoral’ of the story was presented in a song form. This was included in LBT 3, 4, 7, and others, and isn’t really a bad thing at all.
9. Mr. Threehorn/Topsy is no longer as much of a ëhalf-antagonist’ since his love-interest, Tria, came along.
10. Ducky and Spike and Petrie did not know that much about the tinysauruses when they first met them, and Mr. Threehorn was pretty strict on the finding of the tinysauruses, so it was only reasonable for them to choose to tell Topsy at first. They feared Topsy more than the tinysauruses I guess. If you look on less than a minute later, Petrie and Ducky and Spike change their views about the tinysauruses.
11. Be careful not to take “Girls and Dads” out of context. Also, it’s such a catchy song I don’t see how anyone could dislike it lol

12. When Tria said “I like your dad. I’ve always liked him. And he likes me” some people might think back to Cera’s late mother and question things. Just because things aren’t explained in dialog, doesn’t mean there aren’t reasons for things.
13. It is somewhat likely that Mr. Threehorn lied when his reason for being out late at night was “guard duty”. Not long after, Cera didn’t tell the truth of what she knew when she was asked how “she knew what the tinysauruses acted like.” With all the other stretched truths in the movie, this shouldn’t be a surprise, but rather building up the real antagonist of the film that must be defeated: lying! About Topsy however, he could have been telling the truth, but he could also have been stretching it, and then filling the role after he talked to the gang so that he didn’t look bad, and then believing wholeheartedly in the role that he even avoided Tria’s charms.
14. The really flowery scene at the end might have been too much, but is not necessarily bad.
15. Seeing the gang mad at one character, in this case, Littlefoot, is definitely not an unknown thing in the LBT series, but still may be unsettling to a viewer. I can’t remember the exact movies at this time, but I know for sure that the gang was mad at Ducky, Spike, and Petrie respectively for different reasons, but usually lasting only up to a few seconds.
16. Having ëlying’ and ëtelling the truth’ are perfectly ok for a story. Most of the LBT films had focused on literally saving (not just helping) someone or a lot of people, while learning racial themes, tolerance of hate, and acceptance along the way, LBT 3, 4, 5, 6, 7, and 8 (pretty much) as good examples. In LBT 3, they were saving people by finding water and saving the water; in LBT 4, they needed to save Grandpa Longneck while also saving Littlefoot; in LBT 5, they needed to find green food; in LBT 6, they needed to (initially) save Dinah and Dena (how you spell?); in LBT 7 and 8, they needed to save Ducky. In fact, in almost all the sequels, there is a scene where one character must save another. I think Charles Grosvenor wanted to include those things, but focus more on lessons or themes, as the ëgrand predicaments’ had already been present in some of the previous LBT sequels.
17. Loool watching WHY the gang was mad was so funny. You’d think it was because of the lying, but they were in fact mad about all the tree sweets being eaten and not being able to have any, Littlefoot making friends with the tinysauruses and so then the grown-ups more likely to have found the tinysauruses, that the grown-ups got so mad that they knocked rocks down on the hole (misconception by Ducky), and that… Spike ate (or ëet’ as Petrie would say) Petrie’s tree stars haha. They still stay mad at Littlefoot for those reasons though… not for too long however.
18. Littlefoot understandably was mad after his friends continued to stay mad, because Littlefoot had taken all the fear and pounding from finally telling the truth, and had reconciled himself with what he had done, but the others hadn’t, and I think Littlefoot was unable to see that in the state he was in. And still, remember the rest of the gang was mad that they couldn’t eat tree-sweets and stuff, not, as far as we know, that because Littlefoot had lied, lol. Remember, they’ve been through so much together that forgiving Littlefoot should have been an easier thing for them. Still, not much later, they’re all bawling for being mad at Littlefoot :3
19. The colors of SOME of the extras (characters) were of purer hue.