Hello,
My suggestion is to add a queue system in-game to allow players to easily join a server when a slot becomes available.
This system would be included in the server browser, which in case that a server is full, will ask the player if he wants to queue for it, and if so, it adds the said player to the queue.
This would avoid ENTER key spam / annoyance to join a server, and provide a fair queue for everyone who wants to join.
Thanks for reading!