My take...
I would not describe Goff as “mediocre”, as some here have said. To use the word “mediocre”, I’d think of Case Keenum. Case was a solid competitor but with a limited range. Not a huge amount of variation between his best games and his worst.
For Goff, IMHO “inconsistent” is a more accurate word than "mediocre." With Goff in 2020, I still see plenty of signs of why he was called “the natural” as the first pick in the draft. In SOME games he’d display great touch on the ball, and also marked improvement in his ability to throw on the run. How’d he look during that blowout 37-19 victory over the Eagles? Or the 30-10 demolishing of Washington? Or while crushing a solid Bears team 24-10? Or beating up Seattle? Or during that furious comeback against the Bills? Or defeating a solid Tampa defense without having a run game?
OTOH, how'd he look in those two awful defeats vs. SF? Or against Miami? Or when he makes horrible throws and horrible decisions.?
If he were just mediocre, it would be easier to dismiss him. But he's not, he's inconsistent.
In summary:
Good Goff Good.
Bad Goff Bad.