I think the problem for me regarding Toy Story 4 is that it didn't really serve a purpose like the other three did. The Toy Story films have always been about the relationship between toys and their children, and have explored how not being played can badly effect a toys psyche.
The three films were always about exploring different aspects of neglect: the first one was about popularity among toys. The second touched a little bit on natural decay, and made the characters realize that there will eventually come a day where their children will abandon them. The third was about that day ultimately coming, teaching us about letting go and learning to begin the cycle again with a new child.
Toy Story 4 didn't explore any of that. It didn't even explore anything to begin with. It kind of just loosely touched on neglect by children without actually going into it.