To an extent, most successful QBs are system guys. There's probably only a handful of guys that would've been successful anywhere....and they all have a bust in Canton.
Look at Brett Favre now, without much surrounding talent. Does he suck as a QB now? Or does some of it have to do with a lack of surrounding cast?
What about Steve Young in his Tampa Bay years?
What about Jeff George looking like an all-pro in Minnesota when Culpepper got hurt a few years ago......yet now where is he?
Is David Carr that bad?
Why is Joey Harrington having so much success all of a sudden?
Is Brady getting worse, or is his surrounding talent leading to his more frequent INTs?
Becoming a great, successful QB in this league, IMO, has a LOT to do with the right talent going to the right spot (team), playing in the right system (coaching), with the right complementary talent. And I think this is true for everyone, Aikman, Marino, etc.
As for drafting someone, we DEFINITELY need to draft someone at QB. Every team has to rely on a backup at some point and you always want to have someone young who is developing behind the current star. We made the mistake of not doing that with Aikman and it cost us about a decade of non-competitiveness.