Not sure what a "probably" level is, but the way they are coaching up the defense has produced below average results for several years, and they've shown repeatedly that they cannot adjust to how other teams are taking advantage of them.
The excuse of a complicated scheme is hogwash. Of course I don't expect rooks or 2nd year players to master a defense, but that isn't the issue. The issue is that teams have figured out Pete's defense, no matter who gets plugged in, and he is unable to adapt. This is probably why they aquire good players from other teams who all of the sudden get abused in this defense, there's already another thread and breakdown that proves this.
Pete struck lightning in a bottle in the LOB era with some incredible drafts and player acquisitions, combined with a great supporting cast of coaches, and a defense that wasn't figured out yet... at least with the players he had. The rules have changed and the league evolved, but Pete has not. He's obviously trying to change things, I'll give him that, but so far he has failed to adapt.
So you go ahead and delude yourself and act like they just need more time when we have 5+ years of abysmal defense, and a horrible performance against a Rams team that has a bunch of young players and JAGs