the late 1990s were dark times and dark films were successful.
I think my answer to the original question has been posted already. Insurrection was too episodic and not epic enough. It had a good premise, also as described in this thread, but the execution was small and juvenile.
Again, as mentioned, Stewart's and Spiner's meddling in the creative process was not helpful especially with Nemesis. If Data sings, the movie is pants. Nothing about Nemesis made sense, not the Romulan clone plan, not B4, not the motivations...