The problem with the wide 9 in today's NFL is the need for sound assignment played football. Look at the Eagles bucking the trend and winning the Super Bowl last year. Albeit holding on for deer life at the end of the game. But when they were executing it, they were tough to beat. It not unstoppable. Good coaches are able to exploiilt the openings in. If we struggle to open the year Gase needs to jettison Burke and retool the whole scheme. We should bot be losing games because our DC does not want to adapt
Also it creates gaps along the front that are very predictable and manipulatable. That leads to easily creating running lanes.
The gain from the wide 9 is outside pass rush, and possibly easier setting of the edge, funneling play up the middle to the linebackers. The loss of the wide 9 is that it really makes it easy to get to the 2nd level in the run game, and puts a lot of stress on your linebackers to stop the run up the middle.
Compound that with today's preferred system of going with all gap-penetrators, and we get huge run lanes and completely unprotected LB's. With LB's able to easily be moved by pulling guards and centers, it requires good stack-and-shed LB's, and they're almost extinct at this point. If you have those LB's, then there's no way they can cover the short pass--which is the staple of most offenses today.
I like funneling the runs inside, but it puts a huge strain on those LB's. To make that work, those edge rushers need to be getting to the QB regularly, or else the QB can easily carve up that defense by throwing underneath. Just like Flacco did to us the last time we played the Ravens. We don't have those elite LB's to make that work, so we need Quinn and Wake to dominate, and disrupt that QB's rhythm.
As a system, I think the wide 9 is a bad base system. I'm fine with it on obvious passing downs, or to flex a particular end out wide (but preferably not both ends), but it exposes the defense a lot, which is very problematic. We're seeing it every day with our poor run defense and inability to stop the short underneath crossing routes and passes to the TE. A lot of this stems from our choice to employ the wide 9, IMHO.