Not buying this for a second. Totally disagree.
FIrst, back when BYU used to thrpw it all over the place, defenses were built much differently. Safeties were quasi-linebackers that focused on run support first, pass D second. Plus, the BYU offense was new on the scene, so teams struggled to defend it.
Today, defenses are built for speed with corner play being way better, and safety play defending the pass a million times better. A great passing game surely helps, and BYU;s needs to improve, but balance on offense helps teams win.
For reference, see the 2011 Green Bay Packers SB team. Early in the year, they were throw first and had almost no run game. Then, they started playing their 4th string RB who caught fire, ran off multiple 100 yard games, and the Pack became unstoppable. Why? Balance, that's why. You need a run game to win, to get the tough yards, to kill of games, to score in the red zone. You need power running. It is essential. And we are soft.