If you're just asking how to avoid overpowered decks just because of the ability to print proxies, people with big budgets (or a long history of playing) can get all those actual cards already and there's banned and restricted lists for each format (and the formats themselves also help, as they limit which sets are legal, so standard doesn't have to worry about interactions between new cards and every single card made in history).

And for more casual games (that ignore ban lists or allow custom cards), there's the whole dynamic of "if I always play my deck that just stomps everyone by turn 2, eventually no one will want to play with me, other than to throw their overpowered decks at it, so I'll save the extreme ones for special occasions".