The offensive line does not allow receivers to get open, that's a myth at best. I played receiver from grade school to high school, and me getting open had nothing to do with what the offensive lineman on my team were doing. You can't get handled off the line, then be blanketed, then deal with over the top help and somehow run through your route and scramble open. It doesn't happen. Sometimes you can find a hole, but that's happening on a consistent basis. You have to beat your man, simple and plain.
It's part of the equation, I didn't say it was the entire reason. Give a QB 5-7 seconds to throw and I guarantee you'll see more open receivers and completed passes than throw aways and coverage sacks.
Fwiw, I'm not discounting the need for skill players, simply saying you must have a proper foundation to get the most out of them. The OL is the foundation of the offense and DG agrees.