I get what you are trying to say but, its difficult for me to compare the weapons that we have (or lack there of) to what New Orleans has. Ive watched a couple of Saints games and no one crowds the box with 8 or 9 on them. New Orleans has too much to do that.
I was just using the Saints as an example of a team that ran/runs good screens with dangerous RBs. Ultimately the ability to run screens comes down to the OL, QB and RB all handling their assignments - as well as TEs and WRs being able to block.
Crowding 8 or 9 in the box just makes it easier to defend the run and the screen. IMHO.
If the D is staying home and playing the run - sure, it's easier to defend. But if the offense executes correctly, they can still run screens. And if the D blitzes, that's when things like screens and draws are most effective.