Most of the time, these “gender neutral” bathrooms are just single-person bathrooms (one toilet, one sink, locking door, etc). Nothing wrong with those, though it’s a bit silly to call it “gender neutral”
The Washington DC Metrorail system has “gender neutral” toilets ~ into which only one person at a time will fit!
The problem with “gender neutral” bathrooms is men and boys peeing on the seat! I know, I have a few in my house!