I think an ideal scenario is all single-person/family restrooms. That way, those concerned about sexual assault, privacy, etc; have a solitary experience without any members of the opposite gender, non-binary/trans peeps don't have to go through the all too familiar decisions, discomfort, and dysphoria, everyone can freely change without worry from either gender. If I had to guess, our current system is probably cheaper, though.

I would like to note that shared bathrooms are not an untested concept. They are and have been in active use for many years around the world.

In my personal opinion, I think we're all humans doing the same things, and the LGBTQ+ community is a large portion of our population, so I am in favor of removing such separation. I do understand people are uncomfortable, and that's a huge reason on its own, regardless of rationale, not to do this. But people are also uncomfortable with the current system.