"down years" could get a lot worse than 19-24 wins and dominating state rivals.
Sometimes things ebb and flow, and BYU has always needed rosters to line up to have truly special years, I think Bronco would've been back to the top 25 in 2016, despite many thinking he could never reach above 9 again. New blood doesn't mean the ceiling gets any higher. In football we've had MUCH lower lows and lower highs. Didn't take long for the bar to get lowered.