Bullseye!
Quality depth, the operative word being "quality", is absolutely essential in this league, cause at some point you need just about everyone on your roster to contribute. Guys will go down just as sure as the sun rises at dawn, and if you don't have people who can step in and produce at a fairly high level, thats usually the difference between making the playoffs or not making the playoffs, assuming you had a playoff caliber team to begin with.
But its not only that, this game is so taxing and this league is so physically demanding that best case scenario allows you to rotate players without missing a beat, so everyone stays fresh, which can only be done if you have quality depth and you are not taking a big dip in talent when you rotate players in and out.
Over the past few years our depth has gotten worse and worse, to the point where we had a bunch of backups throughout the roster who were not even NFL players in my view. At best they belonged on somebodies practice squad, and we were one injury away from these guys getting significant playing time, and when they came in to give the veterans a blow, the drop-off was as steep as a canyon.
This was totally lost on Idzik, but Mac gets it and he is stacking this roster with quality depth. He added some impact players like Revis and Marshall, some quality starters, but almost as important he has stacked this roster with quality veterans on one year deals, guys who can give you a fairly high level of production in backup roles or start in a pinch if someone goes down without turning a strength into a weakness. These are some shrewd one year deals that will pay dividends over the course of a 16+ game NFL grind.
I look at the depth chart right now, position by position, and I see a team that is light years ahead of what we had last year or the year before that. Now I see a roster than can sustain the war of attrition that is an NFL season.
PS. Don't sleep on the Bowen addition too, if he's healthy that dude can play.