Mahomes is sitting at 4% this year. Then it jumps to 17.2%, 20.8% (!!), and 17.3% per OTC. Though I'm not sure how accurate those numbers are because I assume that's based on a projected cap figure. In any case it will be interesting to see if the Chiefs continue to do well over the next few years.
As for Rodgers at 14%, yeah, that's a lot. But half the QBs in the last 10 years who won had over 10%, so it's not an astronomical amount. If it had been a little less each year for the past 10 years would it have changed things? Maybe they could have kept a veteran player or three around... But a lot of their issues have simply been bad luck (IE: Bahktari getting hurt, Seatle special teams meltdown, facemask fumble back in AZ, etc), so I'm not sure how much of a difference it would have made.
For context, in 2020 it was 11.3%, or roughly the average of what Tom Brady made in the last 4 Superbowls he won.