First, lets get this clear, nobody is arguing to remove the ineligible receiver downfield rule. They're arguing to keep it the same and enforce it. If you're more than 3 yards down field and not engaged with a defender, you should be called for it.

Now, you can't say it kills run support. Oregon, Arizona, Auburn, Georgia Tech they don't faceroll everyone they play. They lose games. They get tackled for losses. They don't run the pop pass every play and win. The play can be, and has been, stopped. Several times per game for every team that runs it.

It's also an option play. The force player being required to make a decision is a staple of triple option plays. Eventually someone has to make the tackle, and the offense is going to work as hard as possible, through reads, to delay that to the furthest defender from the play. This works on pitch options, bubble screen options, pop passes, etc. The principle isn't any different.

The defense has to look at how the offense is exploiting them, come up with a defense for it. There are defenses for triple option teams. There are defenses for pop passes. There are defenses for bubble screen options.

When we(HS) play triple option teams, we have the defensive end take the QB, the playside backer take the pitch man, and the backside backer take the RB. Our defenders don't have to read the play. They have an assignment. If you come free, you have your man. It's not quite a day one thing, but it's up there. Teaching kids their assignments different from the traditional prepares them for the reality of the offensive game these days: you have to be able to, from your base defense, and really, every defense, play the option.

That does NOT take away other coverages. It merely makes your first assignment different. By doing this, you force the other team to switch to other plays. They'll try to lull you to sleep with misdirection and stuff, but that's assignment football. It's a fundamental. And it works.