think the biggest issue is offensive scheme. If talent were the issue, the guys that left wouldn't be starting in the NFL. I can remember years ago people talking about the lack of a great ground game when we had Martin, McGlinchey, Nelson, etc. Occasionally, an RB would bust one but I remember a lot of run plays going for 0 to 1 yard. Wtf?? They go to the NFL and these guys are studs. It has to be a combination of Kelly's offensive scheme/formations and probably technique which still has a big imprint to this day since Rees is running the show. Our O line hauls are always ranked very high. Can't imagine the recruiting services all missed on these guys. The talent is there and they are experienced.
I would agree the biggest deficiencies where ND isn't as talented or deep as some of the other big programs is QB, WR, MLB. QB is deficient period. WR has talent but just thin with the depth and experience. MLB's are slow.