The analogy between a private messaging service and a bar is not just strained; it’s nonsensical.

It might work for a chat system that’s mainly public and discoverable like Matrix, IRC, or Discord. A community having too many people, or any people who don’t follow certain norms can make it unpleasant. As long as it keeps out spammers, Signal having people I don’t want to talk to on it won’t affect me at all; I just won’t give those people my phone number or username.