This doesn't seem complicated. If a receiver runs the wrong route then he either did not put forward the effort to learn the plays, or has a learning disability. Either way it's imperative to get to the root cause, then take an appropriate action. Maybe there is a toxic attitude problem in the receiver room.
I see this as somewhat separate from coaching a receiver. If the potential isn't there send them to the portal. Obviously speed is necessary. Next time recruit better.
That is different from a skills issue, which can be coached based on the receiver's potential: Can the receiver run a crisp route, use his body well, shield himself from the defender, and make a high percentage of catches? I see these things as coachable. Our group was lacking.
In my view, simplification helps receivers but the real benefit is for the quarterback. When you start seeing a QB regress, after coming with great fundamentals, then something is terribly wrong. You don't have a good system to match the QB, which obviously must take into account other team weaknesses and strengths. How is it that some schools routinely produce first round quarterbacks, even Heisman winners, while other schools of equal prominence have little success?
I still wonder how we can put offensive linemen in the NFL while at the same time, as a unit, be unable to pick up stunts and blitzes. Something is very wrong there, and it's been going on for a long time. Linemen blocking the wrong people and not seeing the obvious. In this group we had a great LT, but not on the other side. Being short of a complete line has been typical. In the middle the better teams could beat them and pressure Allar, one of the reasons we failed to win our big games.