He's a generational player...of course he will. It's not like this guy will be playing for the Saskatchewan Roughriders in three years. But take a look at Aaron Rodgers career, and especially at the advanced stats (not the passer rating.). Despite all his talents, due to stubbornness, long slumps, inability to adjust, too much freelancing, he has had a lot of years where he's been average. Look at his adjusted net yards/attempt (ANY/A) and how inconsistent it is. Huge fall in 2012 and 2015; from 2017-19, he's maybe even below average. He relies now on a ton of great support because of his habits, obsession with hero ball, scrambling, etc.
Now look at Mahomes ANY/A. It's not bad yet, where he's a middling QB like Rodgers, but it's ticking down, and this is with a great supporting cast around him, no injuries, etc. Due to the big stats, accolades, TD/INT ratio, passer rating, we tend to overlook things like this, but they correlate with yards/play factoring turnovers, INTs, and the team's overall ppg. He's almost a full yard down on yards/play this year from last year. That's a big deal.