Goff is still sitting halfway through the season. Either:
A) Fisher is stubborn in his belief that Keenum gives him the best chance to win or he and his staff still cannot get Goff ready.
Fisher doesn't want to set Goff up for failure by putting him behind a below average OL and a non existing run game.
C) Goff is not what they had hoped he would be; not a #1 pick overall.

Choice A - that's on Fisher
Choice B - Fisher was in charge of building the OL and the run game
Choice C - Fisher was in charge of the draft