This research was spurred by another comment below, but I figured it was worth sharing it as a separate point.
I went through last year's Top 10 teams and calculated each team's share of WR catches & receiving yards that went to sophomore and freshmen WRs (per Sports Reference's 2020 rosters). Here's what I found:
1. Alabama: 37% of catches, 33% of yards
2. Ohio State: 58%, 55%
3. Clemson: 35%, 32%
4. Texas A&M: 75%, 81%
5. Notre Dame: 0%, 0% (not a typo)
6. Oklahoma: 73%, 77%
7. Georgia: 88%, 92%
8. Cincinnati: 22%, 20%
9: Iowa State: 26%, 26%
10: Northwestern: 12%, 11%
Weighted average, excluding ND: 45%, 45%
Notre Dame (again): 0%, 0%
One other thing that stands out about the list above is that the truly elite programs got more production out of younger players than the "scrappy" squads (Cincy, Iowa State, Northwestern). I guess that makes sense, considering blue-chip programs tend to bring in guys that are ready to play early on, while scrappier programs tend to need more time to develop their players. This makes ND's numbers look even more out of place.
This is, and has long been, a big issue for Brian Kelly.