Aye, it is such details along with some improbable solutions (e.g. using a volcano as an elevator), illogical timing (e.g. these flyers seriously didn't reach that volcano in the time it took the kids to get there even though the flyers had a lead of like half a night and half a day), strange coloring (e.g. green lava), deus ex machina solutions (e.g. Star Trek Rainbowfaces) and serious plotholes (why exactly did they abduct Ducky to begin with? They had absolutely no reason whatsoever to do that. Had Pterano announced to the assembled adults in the valley that he was going for the stone of cold fire to rule them all he probably would have earned himself a collective shrug and an "be off already" from Cera's father. Abducting Ducky was really the one way to ensure that he would be pursued eventually) are aspects that kept a movie with some really great ideas (e.g. Pterano's past) from being great altogether in my opinion.
I'm sorry but I have to tear this one apart
You denounce a few things about the movie but can you tell me what they could/should have done instead?
Let's start with the volcano. Do you have an alternate idea how the gang could get up that mountain quick in order to be there prior to Pterano, Rinkus and Sierra (who could have been there within an hour but what would the movie have to gain from them being there a day before the gang even arrive there? The story would have had to change quite a bit!!! The whole scene on Threehorn Peak just wouldn't be possible since the Flyers would have found and *used* (failing obviously) the Stone of Cold Fire already!)? The idea (of the Rainbowfaces who are interesting characters!) is actually quite cool. Remember this is made for kids, not for our small group of adult fans. I was pretty amazed by that geysir they used to get to the top as a kid... Whether that is actually possible or not, is not a convincing argument, considering that dinosaurs actually can't talk or perform certain movement that the actual dinosaurs couldn't. This is fictional so it mustn't necessarily be tied to things that only work in reality.
Now an alternate way to get up there let's see... they could climb like in LBT 8 where they climbed up the Great Wall from the Mysterious Beyond. Would only take them a while and the flyers would have to sleep very long (or the gang would have to get up in the middle of the night), otherwise your complaint about the flyers taking too much time would be even stronger! So it was good they took a shortcut!
Strange colouring... okay I get that it shouldn't look like that but seriously what is so bad about that? There are situations where I can agree with you that the colouring was unnecessarily messed up (eg. during the tsunami in LBT 5) but here it is not annoying at all in my opinion. Quite the contrary, it adds a bit of mystery to the cave that the lava is green. Colours have been manipulated ever since the original movie to convey emotions (Littlefoot probably had at least 3 or 4 different colour palettes in the first movie) and this here is no different at all. The cave is mysterious and the animators made it shine in a green hue, including the lava which is also green, to suggest just that. Same with changing to red when there's danger (though that's been done to excessively!) or the green sky in LBT 8 & 13 in the Mysterious Beyond. In short, ain't a problem for me

You're complaining about deus ex machina solutions? Well, they're everywhere in movies, you know? Like I said above, find a better solution before ranting about the movie unnecessarily... one can rant all day about various things but ranting won't help you, finding solutions does

So what should the gang do to get up that mountain? Should the Rainbowfaces not exist altogether or be reduced to meaningless background characters because they are delivering such solutions?
I agree that there are many obvious plotholes in some sequels but the one you point out really isn't a plothole... Nobody knew if the Stone had the powers it was predicted to have but I'm sure the grown-ups wouldn't just let Pterano gain that possible power. Even if it's just non-sense (as it turned out later on), could they risk that Pterano might gain huge power in the event that their doubts turn out to be false? And even if the grown-ups didn't think that way, I'm sure Pterano wouldn't want them to know what he's up to. After all, he claims that he would like to prove the righteousness of his actions and be accepted in the Valley again. Now setting off towards the Stone of Cold Fire is one of the most suspicious things Pterano could have done so it would be better if the grown-ups didn't know of his journey alltogether! But then Ducky comes along, hearing information that would make the grown-ups VERY suspicious. It was only logical that they had to prevent her from passing on that very information to the grown-ups... only the way they did that was anything but helping. They should have knocked her unconscious or tied her beak together so she couldn't alert the Valley. Nobody would have known what happened to Ducky or where she is...
I doubt Mr. Threehorn would just shrug when Pterano showed up to tell him THAT! I'm not sure but I don't think Pterano would be tolerated in the Valley whatsoever. At the point of the kidnapping, Pterano was believing that none of the grown-ups (aside from Mrs. Flyer) knew of his presence to begin with...
Pterano did have valid reasons to order the abduction of Ducky so it's not a plothole! This could be discussed further in a separate thread... [EDIT: Here you go!
Here you go!]
Now a response to the original post of this thread:
I'm completely with you on that one, Lone Dragon. I never thought about it this way but indeed Petrie's Mother should have intervened!