I think it is really myopic to say if Goff fails we are set back X years. We drafted Goff to be a starting QB. IF he fails and we find another starting QB Mannion or other we are not set back more like we just didn't get the pay out we wanted. If we end up with a solid starter that will work. A QB for a QB.
Just to be clear I believe in Goff and am fully behind him and think that this year will be the only real sample of his ability. Last year will hopefully be just a jump start for a successful upcoming season.
What, replace him with a guy who is also not the answer?(If Goff fails) It's not myopic to say that the draft capital used to move to #1 overall slot is not easily disregarded, nor was signing guys like Woods, (re-signing) Austin, and hopefully re-signing Donald, Ogletree,and Watkins etc....All the moves to improve the team, just takes us to 7 wins or so without a franchise QB...Mediocre doesn't put us in a position to draft the best QB in the draft, unless we give up even more high draft picks.
It is a disaster if Goff fails, which is why when #1 Overall pick fails (and the time it takes to see that he is a BUST), it may be a few years until you are in a position to pick the next guy to really be a replacement...unless you get lucky.