in his first 6 seasons mahomes had 5 very good/great or all timer type seasons, and his "off" one was still a career year for most nfl qbs.
in his past two seasons he had a superbowl win, and a super bowl loss, but his production has fallen off a cliff. his best games, by far, came against a lay down bills d in the playoffs, so he's not close to shot yet, but the trend is clear.
so far this year he's had a lack of talent around him and has lost two games to really good defenses, but he plainly doesn't look like he did 3 or 5 or 7 or whatever years ago.
i think we've seen his best and his worst is yet to come.