I really want to compare Rex: A Dinosaur's Story to Jurassic Park, because they came out the same year, but it's got more similarities to another Steven Spielberg film: E. T. the Extra-Terrestrial. A kid who has issues with a parent befriends an adorable but similarly lonely creature, and then the kid works to help the creature. Doing some reading into this, both also had creature/special effects done by Carlo Rambaldi.
It starts slow, but once the dinosaur is introduced, it manages to be a lot more fun. I think the simple second act was my favorite, but I did quite like how ridiculous it gets in its final act. There are action scenes, so much slapstick comedy, charmingly not-great special effects here and there, and it also becomes a Christmas movie.
It's all silly, but I found a lot of it very charming. And to say that about a kid's movie I didn't grow up with - and as someone who turns 29 in less than a fortnight - I think that's saying something. Maybe not much, but something, and something's enough. Rex: A Dinosaur's Story is enough.