A triangular shaped metal sign on a pole near where Marsha Johnson's body was found is titled Queer Spaces and explains who she was and how she died. This sign says a lot about this film--spaces. So many spaces exist where we learn nothing about Marsha's life or spaces where files about her case have gone missing, spaces where we get a glimpse of a person's life in her 20's and then only a glimpse again when she is in much older (true of Sylvia, Victoria, and many others).
The compelling aspect of this documentary is the character study of the unflappable Victoria in her investigation and Sylvia Riviera, who hits the bottom and comes back to be a great activist. Both are more interesting than Marsha herself--at least what we learn of Marsha in this film. The scenes where Victoria shows us photos of herself when she was young on stage and Sylvia getting a job at a church are wonderful.
One big space is the lack of resources put into investigating the violence against trans-gendered people--Victoria's boss notes this toward the end. The spaces are the questions always left unanswered when someone dies without reason.
Basically, the movie's title is misleading. It's not really about Marsha, though she is a part of the larger story. It's about being trans-gendered in New York and how this has changed and not changed in the last 50 years.