There is a learning curve
his name is Baker Mayfield, Josh Rosen and Sam Darnold
I wouldn't even say that.
Mayfield is falling off due to preseason expectations. He was good last year, and all the Browns did was add more offensive talent. He crumbled under the pressure when he probably should have been an MVP candidate.
Besides that?
What Mahomes and Lamar have that Rosen and Darnold/Allen (to an extent, because the latter two have been aight but nothing earth-shattering) did not is coaching.
Mahomes has one of the game's greatest offensive minds in Andy Reid.
Lamar has Greg Roman (we saw what Kaep did with him as OC) and a team that was committed to building an offensive scheme specifically designed to play to his strengths.
Not enough coaches play to their guys strengths. Good coaches do that.