It lost its way from 1 and 2 imo. The quantum realm is not a good place for the story to be set as a primary location. Originally in the first movie the idea of shrinking to sub-atomic was interesting although I had to set aside all logical considerations, and not think about that as in how big are atoms and how can you continue to function if you shrink down to atom size? I just avoided thinking about it.
Then Chap 3 came along and rubbed my nose in it, thinking that the quantum realm could be populated with all sorts of little people who live there, having tribal wars as a matter of routine was creative, but they did not succeed pulling it off Imo.