Why isn't it better?
1) We went 2-3 years without headlining LBs in our recruiting classes. I'm not aware of any great LDS talents on which we missed out, and landing the great, athletic, non-LDS kid is pure bonus when it happens on occasion. There weren't many, or any, star LBs to go and get.
2) We've been getting beat for top DL talent fairly consistently by the Utes for a while. Some of it is the BYU dynamic (academic, honor code-related rigor), in other cases, we've just gotten beat. It's began taking a bit of a toll.
We're starting to collect some promising rush DE types, which generated the summer chatter about a 4-3 switch. We have some promising young LBs on missions and coming into the program. There are good young DBs, and we've had recent success in landing JC talent here too. It could come together in 2-3 seasons that you see some very good defenses in Provo.
But in the end, it isn't that hard to figure out. BYU has a tight recruiting dynamic. Our demographic has to first produce talent, then we have to land and develop the great majority of that talent. It all has to come together for us to have a chance at greatness, and it's a tough proposition.