Toy Story 4 is more than sufficiently entertaining, but it doesn't cover much ground that we haven't seen before. What is different is the introduction of the character "Forky", which is a toy made from recycled trash. Forky suddenly comes alive and is not very comfortable with his new existence as a toy. He thinks that he is trash, which technically he is. This raises uncomfortable questions about how life works in the Toy Story universe, such as why are the toys alive at all? Strangely enough, the movie even asks that question, without giving us an answer. Is the film trying to get us to think about something? We could raise this line of thinking to a much higher existential level and wonder why we exist at all?
In the first film, we accepted that the toys are alive as part of the magic. The Toy Story movie was a new technology that felt magical. Toy Story 4 is darker, similar to the third film, so somehow the magic isn't quite the same anymore.
Part of the problem is that the story is just not as strong. The first film gave us great character development that came out of a conflict that really seemed to matter and was resolved in a very satisfying way. Here, not so much. The movie is mostly an action film with a touch of character development on the side. Fortunately, the movie also knows how to touch our hearts, but again, this not that different from what we have seen before.
It feels like the movies have run their course because they have already done everything that they can do. Despite this, the ending leaves open some questions about what is going to happen to these characters that may require yet another movie to resolve.