Rose is great. He's arguably the best coach BYU has ever head. That said, people can still find themselves in a rut.
I'll draw upon my own professional experience. When starting a new gig, I attack it hard. I put a lot of energy and effort into it. The results, follow. I've noticed, though, after a few years once the routine starts to settle in the foot comes off the gas a bit. Occasionally, a big project or something will come up and I'll hit it with all the energy as before. I think this is a fairly common phenomenon, one that I feel Rose may find himself in.
We're not seeing the same Rose we saw in the first half of his career.
There are a bunch of excuses as to why we're slipping - different conference, change in mission age, lack of a bench, etc. People who are comfortable, people who have settled, lean on the excuses. They are valid excuses, and past success provides a valid defense. I feel like Rose/BYU is leaning on excuses.
There were plenty of excuses when Rose started - limited recruiting pool, the HC, a tough conference, teams that are familiar with BYU, etc. But when he started, we never heard him excuse his performance. Quite the opposite actually. The excuses were challenges to overcome, which he met head on.
As much as it pains me, I think it may be time for Rose and BYU to part ways.