Players who have not unlocked the features can still play with those settings as long as someone who has unlocked the features is hosting the map.
That's true when playing through the main game, but kszyhoo is talking about CLOT which uses different rules.
So doesn't it make CLOT useless (or at least dramatically reduce it usefulness)
Well, that depends on what you're comparing it to. If you're comparing it to making games by hand, then it depends. If you're making a small tournament (< 100 games) and you don't mind create them by hand, then yes, it reduces its usefulness. If you're making a tournament or ladder with thousands of games, like today's ladders do, then creating games by hand isn't really an option. This is where CLOT is extremely useful.