I think a lot of Goff's being undervalued is due to the modern media age of Red Zone, TikTok, and even just SportsCenter Top 10. Mahomes, Allen, and Lamar are apt to make the flashy play, the play you see a million times from Monday to Thursday. Goff is apt to make the adjustment pre-play that gives him a wide open ASB to put a game on ice, or masterfully work through his progressions and hit his third option in stride. He's so good at what he does, but what he does is not flashy.
Those who know ball know just how elite Goff is. But the average NFL consumer does not know ball as well as they think they know ball.