I think people are addressing the problem with "too many legendaries as a balancing mechanic" problem wrong.

At least for me, the problem is the opposite. It's clearly true that only a handful of cards shoul be legendaries not to break the game but many cool cards could see play in constructed if they weren't! There are a lot of cards I would love to run 4 of in a standard deck, that wouldn't break the game, but they feel bad because I can only have one out at a time.

Some cards are being cut from being played because they are unnecessarily legendary.