Just to use your italicized portion as a jumping off point:
No 21st century RB made the list. If people really want to consider that a problem, they should re-check every RB on the list that they think wasn't worthy, and then re-check EVERY other RB, not just the 21st century RBs.
No-brainer level choices who are not the "old-school" guys from well before the Super Bowl era:
Brown
Campbell
Smith
Sanders
****erson
Payton
Sayers
Simpson
So that leaves only 3 slots where you're even going to have the argument of "not a lock" or "from too far back":
Lenny Moore
Earl Clark
Marion Motley
But, even if you take all 3 off the list, you still don't just automatically jump to 21st century RBs. There are still all time greats like Marcus Allen, Tony Dorsett, Thurman Thomas and others (Walker, Czonka, Harris, ...) who'd have to be looked at. Hell, depending upon how you were weighting your criteria, you could easily argue for Bo Jackson.
So, sure, there are at least 3 21st century RBs who could be, and likely were, looked at seriously (Faulk, Tomlinson, Peterson). But I don't think that they are clear "mistakes" who'd absolutely and positively have gotten in if only the evaluators hadn't had some theoretical bias against the most modern RBs.
And that's just the RBs. I think one thing we've got going (and understandably so) is people with recency bias claiming that those without it are biased, while ignoring their own.