(Wow, this is going to be my first big post about the LBT series on the Gang of Five in...must be 5 or 6 years

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Now that you mention it, I don't think I've ever really seen a topic that really digs into the similarities between RAS and Grosvenor's sequels. Good call.

We often see topics about their differences and the likes of "I don't like XYZ about Grosvenor's style"...
The question then is, why? Why do we give this so much thought if there is so little difference? There must be enough difference that we're picking up on it. Since we're picking up on it, naturally we are bound to gravitate more to one style than the other for various reasons.
To be fair, a big part of it for our older members (like myself, 29 years old) is likely nostalgia. We're so fond of the films we grew up with that the others just don't quite touch them. Like anything else that one knows intimately, one is going to pick up and amplify subtle differences, perceiving them as greater than perhaps they are from an objective point of view.
From my biased point of view, LBT 5 and later all mildly annoyed me because of the differences caused by the switch of so many elements simultaneously.
To list the most prominent for me:
1) Cera's voice actor.
I absolutely adored her voice actor in LBT 2-4. Losing that was so heartbreaking to me and the newer one never did grow on me. I've grown to accept it but at the end of the day I still miss her voice in LBT 2-4.
2) Character writing.
Honestly, there were more than a few changes in characters' dialog that I picked up on pretty fast.
For example:
Cera no longer says "heee" with the big grin on her face. Cera in general became...I'll just link to a massive post that I wrote on this topic years ago rather than re-write it. You did mention in your post that Cera became more aggressive and that's what my post primarily focuses on.
Does Cera seem angrier after LBT 4? (That post is 9 years older than this one so bear with me.

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Ducky starts using her "yep yep yep" thing in other contexts: "yuck yuck yuck" being one example. She never started doing this until LBT 5 onward (I haven't watched the films in ages so I can't recall many other precise examples of this).
Grosvenor seems to run with and play around with the characters' gimmicks more than RAS did.
3) The CGI openings.
My first impression of Grosvenor's work was that damn CGI galaxy at the beginning of LBT 5. Between that and the pretty horrible editing error found within the first few minutes of LBT 5, Grosvenor left a pretty poor first impression on me, which I'm sure didn't help my bias.
4) The introduction of more and more fantasy elements that feel out of place compared to the earlier films:
- The Lone Dinosaur character
- The Stone of Cold Fire
- Aliens (really?)
- Dreams shared by all Longnecks
- Great Day of the Flyers (dinosaurs have holidays now?)
Grosvenor quickly (by LBT 6) drifting away from the simple innocence that made the earlier films work and stepped into wilder and wilder territory. A damaged wall or a drought was no longer enough to hold a film.
...Now to be fair, LBT 4 had the fantasy element of the night flower. I will acknowledge this but I do feel there is one major difference between the night flower and the later fantasy elements:
The night flower is a concept that fits in a prehistoric world and doesn't rely on any humanistic ideas.
The Lone Dinosaur is based on the idea of a "Lone Ranger" or even superhero.
The Stone of Cold Fire, while ultimately proved to be nothing, introduced the idea of magic.
Aliens are a concept never before considered until the science of astronomy.
The night flower concept is little more than an animal eating something that eases its stomach. It seems much more in-tune with the prehistoric world than the clearly-human-inspired elements introduced later by Grosvenor.
5) Animation and style.
Here is another major difference. At first glance, without remembering which scene a screenshot is from, I can instantly tell whether it's a Grosvenor film or a RAS film. The two have distinctly-different looks.
In my mind, LBT 2-4 have a more "classic animation" look to them, similar to a cleaned-up version of Disney's The Rescuers or Watership Down. It's simple animation with gorgeous watercolour backgrounds that make it appear relatively timeless.
LBT 5 and later start bringing in the use of CGI to compliment its animation style. Even without talking about poorly-rendered galaxies, LBT 5 and later starts to look more like a Saturday morning cartoon and less like the original Bluth Land Before Time. The series is showing signs of evolution in its art style. The brighter colours, while crisp and inspiring, also do present an atmosphere of being intended of being presented to a younger audience.
While this may not inherently be a bad thing, I truly do feel like LBT 2-4 looked more like timeless animation classics when you see them in screenshots, whereas LBT 5 and later do start to look like Saturday morning cartoons. LBT 2-4 were just absolutely DRIPPING with atmosphere with its subtle but effective animation, LBT 5 and later started using its animation and bright colours to yell and scream at the audience a bit more with the art style. Gone was the subtlety; in its place was found more extravagant use of art style. Again, not necessarily a bad thing but the two do convey different emotions to their audience.
6) I don't really feel like I need to address the music or songwriting as it's stayed pretty much consistent throughout the series.
I feel like LBT 5 and later have a more modern and less "timeless" sound in general but there are more than enough exceptions and I don't really have much to say about the difference in the soundtracks. Tavera's music is brilliant and its use throughout the entire series is more than welcome as far as I'm concerned.

LBT 2-4 was a simpler time when all it took was adorably-enjoyable characters and some little thing to get them to hang out together in a slow-paced, simple adventure. I've heard it said that some people consider these to be the most boring films in the series and I can see why. They do tend to have less going on than the Grosvenor films...but honestly, that's what I like about them. They're all about the world and the characters and that's what I love most about LBT.
LBT 5 onward started taking a more dramatic direction and drifted away from the simplicity of LBT 2-4. LBT became bigger in many ways at LBT 5. Is this good or bad? Up to you.
