I don't think the fundamental scheme is doomed to fail. We have seen this scheme produce really good defenses. Sure they still didnt get it done in the playoffs. But it has been effective. And other teams are running it well. The way they are trying to run it at the moment and the way they are calling the game on that side is absolutely an issue.
I don't think we have the D talent to be a top defense. But we do have talent to be better than this.