Wrongheaded thinking led to the idea that running backs are far less valuable today than they once were. They are still valuable, but their usage has adjusted in a pass-first, role-driven league.
A backfield is as valuable as its production, depth and potential.
For too long, many considered a 50/50 split between run and pass plays as a balanced offense. But that's significantly changed as teams have gone from featuring downfield, low-percentage throws to relying on short, precise throws that serve as extensions of the run and intermediate passing games.
Thus, true workhorse backs who were once household names slowly disappeared.