Elite edge talent is rare, and they want to go somewhere they can really roam free. That requires a system where you can play man press and leave your corners on islands. So, it requires elite edge talent and elite CB play. Guess who has elite CB speed? Not white LDS kids, and certainly not very many players who are willing to live the honor code. It's a very unique recruiting situation. It's not something that you can just "go out and do something about it". So long as we have the Honor Code AND elite academic standards for admission, top 50 to 25 is BYU's ceiling.
Imagine having Stanford's academic requirements, and then on top of that you're telling your players that not only can they not have sex, they can't even have girls in their front rooms after midnight.
I think people forget how truly unique the recruiting situation is for BYU. Honestly, it's a miracle they've accomplished what they have.