Yep, it's all about adjustments. If you watch the line of scrimmage with a keen eye (which is what you should do btw to really enjoy the game) and not just follow the ball, you'd notice that the defense shows their hand each time a QB raises his leg up and fakes the snap (in shotgun).
A 7 man front will turn to an 8, allowing the QB to make a decision to not run into a less favorable box and throw it instead or to call a run in a direction away from where the safety is coming from.
Blitzers will take steps forward also, allowing the linemen and backs helping out in blocking to know who to block. A CB will get off his man if he's blitzing, allowing the WR to call him out. The QB will also notice the safety drifting towards the WR being covered by the blitzing CB, allowing the QB to take notice and set up for bigger plays.
I heard the skins don't have a lot of audibles in their offense and it's easy to see why they struggle. Any defense can break down your protection schemes if your offense isn't able to aptly adjust on the go.