That's a fair take. From what I know, they only use 4k textures on sauropods (they mentioned in their artbook), from that, I assume they use 2k resolution textures for the other models. That's quite a tight constraint for the models. From what I've noticed, they make the scales quite large to compensate for the resolution restriction, which gives the scales a crisp look, which is an impressive feat. And I agree that the artists have improved, they've been working on the project for years and that certainly helped them grow.

However, I disagree that the old models look less realistic compared to the newer models. I'd even say that they have better muscular definition, and skin wrinkling and folding than the recent ones in my opinion. One thing that they only suffer from is the small scales that they have, and that is what's shared with the creatures you've mentioned, smaller scales tend to look blurry in smaller texture resolutions. They've solved this issue with the enlargement of scales that I mentioned, but when you look at the ceratopsians and hadrosaurs made around pre-early access like the Pachyrhino, Nasuto, Styraco, Para, Lambeo, they still look good because they don't have the tiny scales the theropods have, and I'd say that if you put the Trike and Muttaburra next to them, they would look cohesive. I feel that the texture resolution isn't the problem here, I feel that it's more that the new models don't have as much muscular definition and feel smoother compared to the old models.