Well, obviously. But CXyz is actually pretty average, definitely not competitive. They are annoying, but the twins are just kinda gimmicky, they're basically the equivalent to a competitive structure deck. Not bad, but not especially viable for much other than learning the higher level mechanics of the game. They've always just felt like a way to introduce new players to the BS that starts happening once you can make your own deck that relies on spamming the summons. I'm sure they're fun if you've got another deck around the same level, but I've always just found them more tedious than anything. As for the broken card thing, decks usually work one of two ways. One, they have a bunch of small effects that shut your opponent down, or two, they have one really strong ace monster and support cards that make it really hard to overcome. The twins definitely fall into the first one, not saying that's bad, my deck fell into the latter, and while it's usually a decent match, twins usually struggle to overcome "boss monsters".