While he doesn't have the arm talent of, say, Allen, few do or ever have. He does have first-rate accuracy and anticipation, which makes up for a LOT for a lack of a 70 air-yard bomb, yet his downfield stats are enviable - he is NOT a dink-and-dunk QB. He can move decently, and it's always for a good reason; he doesn't just get happy feet to show that he can run, and he NEVER panics, as far as I can tell.
His attribute that is TOTALLY elite, and I think is tied with his accuracy as his most important, is processing. He reads the defense and knows where everyone on his team is, is going to be, and when. He has gone through most of his processing while he's dropping back, much of the time. He is a system QB in that KS couldn't draw up a better QB for his offensive style if he had a genetics program going on in the basement of the stadium.
The kicker, though, is that no matter how much he is or isn't a Shanahan System QB is HE GETS IT DONE. All the stats in the world don't hold a candle to execution.
If Ronnie Bell didn't have butterfingers, Aiyuk was playing anywhere near his potential and was even in the same area code as his contract demands pegged his self-assessment, and the defense was playing to 70% of its ability, he would have had historically great numbers and beaten the brakes off Stafford and the Rams. Special teams even showing up would be a bonus, and none of these "ifs" are unreasonable. .
Finally, while he deserves QB1 money, I HOPE that, when the time comes, he will tone down his hypothetical contract demands to allow SF to keep and recruit other elite players. Their SB window with this team is closing and Purdy burns with desire to win. I have a feeling he will, because everyone that's ever coached or played with him says he is team first kinda guy, and he may well be grounded and humble enough to realized that he doesn't need to make generational money every single year.
In case it's not clear, I am a BIG fan of Brock Purdy.