Your reminder is apt, and I'll just try here to make a point of distinction.
No one knows how Goff will work out. No one. Not the boosters. Not the skeptics.
So far, his performance has been mixed. He has shown flashes. He has shown that he is unready. Both sides have evidence to point to.
However, there is one level of criticism that I think can decisively dismissed. The idea that a great QB is defined by whether he is ready to start in Game #1 is simply absurd. NFL history is replete with examples of QBs who have grown into the position. You've named a great example. The QB Goff is often compared to, Joe Montana, did not start for 1.5 years, playing behind the great Steve DeBerg. Tom Brady didn't start until Bledsoe was hurt. On and On. I do not see how anyone can seriously argue that Goff's being unready is meaningful evidence of his limitations.
Now, it is just as illogical to simply assume that he WILL BE great when he adjusts. Again ... neither side knows how he will work out.
What we can do is look at what he is currently showing us. I am a believer that, 90% of the time, great players show you flashes early on. We can look at his current performance and ask, do we see flashes of great QBing?
Of course, different people will see that tough question differently. But, even there, I would ask Goff critics to recognize a distinction.
Most of the CURRENT criticism I see of Goff talks about how ... he isn't ready. OK. But saying that doesn't say much. If he still isn't ready next year or the year after, then it starts to matter. But right now, it's hard to plausibly argue that a rookie coming from a simplistic offense and struggling with the complexity of NFL O's and D's isn't simply adjusting to a very difficult league. I mean, maybe it's more than that. But I don't see how criticism of Goff processing things slowly can add up to much at this point. Holding on to the ball, for example. Is that a character trait in the player or simply the result of a player still figuring out the playbook and being used to playing in camp in a red, no-touch jersey?
I much prefer it when observers--boosters or critics--base their responses on observations of what he IS DOING. Does he have the arm? The accuracy? The basic ability to move his vision across the field? The footwork in the pocket? The quick release? That stuff.
Thing is, I have seen very, very few criticisms of Goof on these levels. I think that it is telling that his critics don't really seem to point to anything other than readiness and confusion.
Well, I like Goof a lot and have high hopes. But I can understand criticisms. I just ask critics to distinguish between readiness issues and indicators of the player's core capabilities.