"Yards of seperation" is sometimes (often) a misleading stat. It's how far the WR that the QB throws to from a defender when the QB throws it. It can be a sign the WRs aren't fast enough or aren't disguising their routes well enough, running bad routes, etc. But if the QB waits till after the WR is open, but the defender caught back up, or lobbed the ball allowing the defender to catch up, or throws the ball short or off target making the WR to go back towards the defender to catch the ball, or throws to a blanketed WR when someone else is wide open that still counts as a lower "yards of separation" stat. Or if the QB throws the ball before the route has had a chance to develop as designed, either because the O-line allowed a QB hurry, or the QB screwed up and panicked that also counts as a lower "yards of separation".
I'm certainly not arguing our WR's are fine. Just pointing out that a bad QB or bad O-line can have a negative influence on that stat. It's not purely a measure of the WR corp.