The lobbies are bugged. This was noted on a bug report I filed.
I don’t know why, but if you get into a lobby, it won’t fill, but if you just click ready and drop, then by the time you make it to the first enemy your team fills. Usually.
Sometimes you get fully lobbies, but usually the match maker doesn’t add people to the lobby, but does add them to the game.
Granted, I’m also concerned on the issues you raise, but this bug is at least part of it.