Let's assume you are correct about the drop off in RB talent from Duke to Yearby. So I would assume that you could also see the OL drop off in talent from Flowers, Feliciano, McDermott (2014) to that of Isadora, Linder, McDermott, Darling (2015). It took Flowers, Feliciano, McDermott three year to put it all together which help Duke get over the 1,000 yard bump. And Yearby was able to put up a half a stack with only 86 carries behind that same OL (2014). And that's in an offense that was not run heavy even with Duke. If you don't like the Guy that's one thing but don't ignore the numbers when they don't support your argument.
Flowers is a beast, but Feliciano was a 4th round pick, and McDermott went undrafted. It isn't like that 2014 OL was stacked.
Here's some stats to consider from 2014:
Yearby - 86 - 509 - 5.9 - 1TD
Duke - 242 - 1,652 - 6.8 - 10TD
Yearby's looks good until you consider that a large majority of his stats came against 4 of the worst teams we played - FAMU, Ark St., Cincinnati, and UNC. In those 4 games:
Yearby - 54 - 344 - 6.4 - 1TD
Duke - 52 - 526 - 10.1 - 5TD
63% of Yearby's carries, 68% of his yards, and his only TD came in those 4 games. Duke had 2 less carries those games, averaged 4 yards more, and scored 4 more TD's & had more yards than Yearby did for the entire year.
Here's their YPC for the year, and just vs ACC opponents:
Duke
2012 - 6.8 yr / 7.6 ACC
2013 - 6.3 yr / 6.4 ACC
2014 - 6.8 yr / 6.5 ACC
Yearby
2014 - 5.9 yr / 5.2 ACC
2015 - 4.9 yr / 3.9 ACC
Against ACC opponents - Duke stays the same, Yearby gets significantly worse. That's why Yearby's ypc dropped so much in 2015. It wasn't the bad OL, it was that he got more carries against quality teams.
Yearby has 181 carries against ACC teams in his career, with 1 run over 30 yards. One. That's really, really bad. In Duke's first ACC game, he had 2 runs over 50 yards in his first 5 carries.
Yearby's stats don't look good, and Walton's stats are even uglier. Elite just isn't a word that should be used for our RB's.