I think Quinn excelled at a few hard to quantify things. On his one-reads, quick throws, etc., he was exceptional not a just hitting the guy but putting it in the right spot to allow for receivers to maintain momentum, keep their eyes up, and get downfield/make guys miss. It's easy to say all quarterbacks can do that, but I would be willing to bet a deep analysis would put him in the top tier of that particular skill. And I think that's part of why Sark schemed so heavily that direction (along with very fast and shifty skill guys). I also saw him make a bunch of reads for developing downfield plays that most QBs at the college level don't see/anticipate well enough to make the play. His ability to hit those shots, though, were up and down, luckily more up than down this last year (4th and 13 woo!).
To me, his MAJOR flaw is navigating the pocket. It's like he plays with blinders on. Can't feel pressure, doesn't step up well, doesn't escape well, and to your point it means he gave himself very few opportunities to create, and walked into sacks WAY too often. If he learns that at the next level, I believe he has the rest of the skillset to be a creative, off-platform guy. But he never did in 3 years here, so I'll believe it when I see it.