I cannot recommend the game either. Even if you like the gameplay, there are several issues with the game that make it frustrating. When I played the week of release, when the most players were likely to be around, matchmaking took a really long time. Finding and getting into a match took at least as long as the match itself. That's no fun. The game also didn't seem to add players midmatch. So when you're playing 3 on 3 and one guy quits because he doesn't like the map selection, and then another guy leaves because he doesn't want to play outmatched, you're left with three guys running around the map hunting one guy on the other team.
I co-sign all those issues. You are right that no one can be replaced mid-match. Also it didn't even support 4 v 4 at lanch. 3 v 3 was the max. No idea if they patched that, but i imagine the community is only smaller now regardless. Not a good game.