I've thought for a long time that these notions of clear SEC superiority were unfounded Internet tripe. I think in some years past it was probably slightly true, these days it's probably slightly untrue. Outside the B1G these days there is a pretty clear dropoff. But in some years past the other conferences have looked pretty strong, to me, top to bottom, just winning an NC doesn't mean your conference overall is great.
The SEC has been through some "helmet rotation" with programs like Florida, LSU, and Tennessee being down, and Ole Miss and Vandy being up (of late), and they don't have the same helmet as the others. I suspect if Florida and LSU replaced Vandy and OM, perceptions might be different for some.