There have only been 2 linebackers that have gotten the MVP since 1957. Yet I doubt anyone would say linebackers don't contribute. If you want to test the theory, go ahead and find a few and tell them they don't matter.
Some roles are flashier, doesn't mean other roles are extraneous.
This analogy is really getting murky as everyone seems to be making a different point with it now. And then answering their own version.
I don't think anyone is arguing that linebackers aren't important. Or that they need to be as "flashy" in exactly the same way as quarterbacks.
People are arguing 2 things:
1) in D&D, Wizards are superstar quarterbacks like Manning and Brady. If you want to play a linebacker (Fighter), though, D&D makes you play "can't remember his name system guy" that certainly contributes to the win but isn't a superstar. If you get to play Manning as a quarterback, why can't I play Lawerence Taylor or Ray Lewis as a linebacker? Why can't I be flashy in a different way as a linebacker? Where are my game changing sacks or forced fumbles or sending a guy off with a concussion?
and
2) D&D Wizards are flexible enough that not only are they superstar quarterbacks but especially at high level can also fill in for and in some circumstances exceed at linebacker, punter, wide receiver, etc. if they choose to. Fighters can only be linebackers.
Some people already believe you are playing Lawerence Taylor as a 5e Fighter alongside Manning but given the examples of mythic martials we have in fiction, I don't see how the current 5e fighter can be thought of as a 'superstar' in their category. The high level 5e Wizard is clearly a superstar in the fantasy magic user category with crazy amounts of variety, power, and usage at very little cost -- almost never seen in fiction except in the super hero genre like Dr. Strange.