The Good Dinosaur was good, just not the top tier Pixar material.
Visually, it might be the best Pixar movie ever. The environments were insane.. truly stunning animation. Toy Story 3, Wall-E, are some of my favorites visually.. but this one was incredibly well done. The photorealistic environments and more cartoony dinosaurs weren't a big problem once the movie got going.
Story wise.. not the greatest. It's much simpler, but that wouldn't necessarily bad a bad thing. Not every movie would be as complex as Inside Out, or tell such a great story with less dialogue like Wall-E, but this one was a lot more straight forward. There's not a huge subplot, minor characters don't hang around for that long, it's mostly just Arlo and Spot. I liked that at times too, it's a simpler, quieter story. Not as laugh out loud funny or filled with visual gags either.
I think the critics reviews are a little "harsh" even though it wasn't panned, I'd put it a solid B to B+ by Pixar's standards. Not even close to the Cars 2 level.. not as bland as Brave either. Just not the elite/top Pixar level. Still really entertaining and sweet.. emotional like Pixar can always do.. and surprisingly realistic about the fear and dangers of nature/the world and the journey of maturing and growing up.