Should tell that to Payton. He came in and took a RB as high as he possibly could. He understood you need playmakers and you can't pass on talent when your team has so little of it.
Running backs are producing at a high level well into their second contract. CMC led SF to a NFC Championship game 8 years after being drafted. Barkley came just shy of the single season rushing record 7 years after being drafted. Derrick Henry is still bulldozing people after 9 years. That's a long time to be able to rely on your running game while the QB situation gets sorted.