is not an excuse for poor character development. I get it, it was a "what if" based around the real events. guess what? so was inglorious basterds.
telling me "well if you only knew about what happened" is the real life equivalent to "well you should ahem read the books then they explained it more"
this movie was missing something. character development but anyone but our protagonists.
For me there just was no takeaway from the film from a personal standpoint. It was also annoying how so many faux-social media movie critics drew the same conclusions about the film's deeper meaning which it never had and instead they explained that the movie was self-examination of Tarantino's own body of work overall. To that I say "so what?". Like you stated, it's so meta and historically referenced but I think Tarantino's subject matter has been covered so many times by other films and TV shows it just didn't feel like we were witnessing a new perspective.
On a personal note, I have been reading a lot of biographical work on Orson Welles during his early years, his heyday as a praised son of Hollywood, and his ultimate banishment by the studio system. There's just so much there that I think a movie or series about Orson would be more intriguing than trying to revise the outcome of Sharon Tate's life.