But...I think that's kind of the fun.
I think of it like Ranked fighting games in which you don't know against whom you'll be playing. Sometimes it's just a counter-pick to your character, it happens, especially in fighters. (Baraka does not want to fight Sub-Zero. Scorpion does not want to fight Shang Tsung. Elizabeth definitely does not want to fight Sho. No one wants to fight Dante for any reason because he has no weaknesses. And so on.)
Granted, matches last a lot longer in ARAM, but I like the challenge if you kinda get screwed a bit. Sometimes we end up with four supports and a fighter.
And sometimes you pretty much win at champ select. I got Blitzcrank once...With Kalista, Lucian, Varus, and Jinx. Yeah, that went as you'd expect.
But it's like mystery skins, kinda. You just don't know how it'll really end up. Even if they "win" champ selection, that doesn't necessarily mean they're any good as that particular champ, you know? I've seen plenty of lousy Threshes and Fiddlesticks.