I have seen fans and some talking heads ask, "Why would McVay take Simpson when he gave up on a more talented QB like Goff?"
I don't think that is an accurate characterization on why he "gave up on Goff". I think he lost faith in Goff's desire to work at some of the basics of QB play, like blitz recognition and and how to counter that and other schemes that teams were throwing at him.
I don't think itvwas a talented issue. It was the realization that he was leveling off, and maybe regressing. Look at the Miami game that year. Also, the Jets game. Goff was making foolish mistakes and something had to change.
If a guy like Simpson is great on the mental aspects of the position, then his physical traits are enough for him to be very successful. Especially, when paired with McVay and Simpson's very good mental approach, running McVay's offense.