It's only because matchmaking has gotten so good that it's even a problem. In the old days you matched with whoever was available and that was that.

Smurfs are also different from alts in my mind at least, an alt is something like a low level WoW character when you have a main that is max level; a smurf is more like Carlsen signing up for a chess.com account under an assumed name to gleefully squish people until his rating gets high enough, then starting another account. It only really works in games where each "match" starts off fresh for both players.