Since 2000 (and including BYU's win vs Utah in 2000), BYU has only beaten Utah 5 times. Utah has beaten BYU 9 times - that's nearly a 2:1 differential!
In that same time period, Utah became the original BCS buster, won the Fiesta Bowl, won the Sugar Bowl, put a player on the NCAA equivalent of Madden, and made the jump to a P5 conference. They are - currently - much more relevant than BYU.
BYU really only "sustained a high level of play" for about 20 years. During that period, they introduced an offense that was very influential, but let's not kidd ourselves; prior to that, they were garbage, and since then they have been - on the whole - fairly average.
At some point, teams have to move past their history and perform well in the present. Colorado isn't a nationally relevant powerhouse because of their national championship (a full 6 years more recent than BYU's). Likewise, Yale's 27 national championships and two Heisman trophies don't automatically make them premier program in 2015.
It seems like you have a case of Dallas Cowboys syndrome - you're convinced that your team is a perennial title contender/top-team, when in reality you're cheering for a fairly mediocre squad.