I voted Xs and Os/coaching. You can coach around a bad oline. You can use quick reads, screens, your TE. Our offense, to be successful with our OC, had to have arguably the most punishing running back and the most elusive QB in the NFL.
When we lost Lynch, we were very inconsistent minus the unreal stretch between Baldwin and Wilson and a nice 8 game run by Rawls. Never did our offensive coaching staff game plan for upcoming opponents and exploit weaknesses. They were simply content with ramrodding the same plays over and over regardless whether they were successful or not.
Keeping our receiving TE in to block almost every play, running constant empty sets on third and short, throwing bombs on every other 3rd and less than 10, stifled any progress the offense could have made.
Russell Wilson did what he could with piss poor game plans and ran all over the place to try to make things happen and at times did a masterful job. Sometimes those broken plays would turn into wins.
I honestly believe with almost any other OC and line coach combination, we would have had at least 2 superbowl wins and possibly 3 prior to our team being dismantled due to salary cap, injury, etc.