Club rooms are set up by individual users, and if they choose to password their room to only allow their friends on it, then that's their prerogative.
Also sometimes competitions password their room so only registered participants of that competition are allowed to compete.
So it depends on the room and who has set it up.
It's probably best to check the club it's from and see if they have a Discord server. If they do, you can probably connect there and ask for the password.