I agree with both of you. Your sense that the difference between Alabama's offense when McCarron was QB to now is like comparing the option to the air raid is correct. The fact is that Alabama only passes the football about 5 times more per game now than they did with McCarron his Senior year. The difference is how the offense is structured and more specifically, what Saban is asking his QB to do has changed. It's not about being a game manager anymore and winning with defense. The rules don't allow for that philosophy to be successful.
However, I tend to go the other way when comparing Mac10 to McCarron. There's a difference, but there's not a gulf of difference. Mac's stats are certainly more eye opening especially when you consider those aren't even Senior stats. He was a Junior and it was his first year as a starter.
But he had so much talent around him - more importantly the best offensive line and best play caller. He didn't face any pressure. Ever. People love to say that about Tua and Alabama QB's in general but in this case it's true. He was never really threatened. The few times he was, like the first play of the game against Georgia - the result was LeCounte's interception.
I think if you were to put all of the QB's in this draft in the same great situation, Mac Jones is still going to look the best. Better than Lawrence, Fields, and Wilson. Because of what you stated - his accuracy is better and he's more consistent with his mechanics. But what I think you have to do when talking about the NFL is project them all into bad situations and decide who will be able to overcome obstacles the best. Mac Jones comes in last.
It's all about the situation they land in, and there's never very many good situations in the NFL for QB's to land.