Truly idiotic take. By that reasoning, we have no idea how any player would have turned out if drafted by a different team, so we might as well just give every GM a lifetime free-pass.
We know for a fact that Mahomes is hands down the best QB in football and far and away the league MVP in his third season as a starter. No matter how Josh Allen turns out, it was a mistake not to draft Mahomes in 2017. In fairness, the Bills did make good use of the picks they got from KC to trade down. And there is also no doubt that other franchises missed the boat far more egregiously, like the Bears, who gave away a ton of picks to move up from 3 to 2 to pick Mitch Trubisky, and the forever QB-needy Jaguars, who drafted a running back at 4th overall that year. But it does not change the fact that it was a major blunder by the Bills and McDermott.