No, the 2018 class is was Frost's first class, the transition class
https://nebraska.rivals.com/commitments/football/2018
The 2018 class had a lot of departures, but it did provide a half dozen guys that are/will be starters now. What that class didn't do is provide quality depth. The 2019 and 2020 classes are building that and have only had a few departures out of over 50 signed players. The 2017 class, Riley's class, where all the 4* left the program or never made it. That class hurt as those players would be RJR or SRs now. That class only produced 1 starter and a few other guys in the top 2-3 string.
Only 1 player from the 2019 class left the program, WR Chase...he wanted to be closer to home. The 2019 class were true freshman last season. Going into the 2020 season there are 19 players in the 2019 class that are expected starters or in the 2 deep.
Funny you mention RB depth as that is one area that is not deep...shows you don't know much about Neb football. It's Mills and a few true FR or RFR. JD was a really good player, but W. Robinson should replace much of his production. The top JUCO WR Manning and top 100 croot Betts should add size to what was a tiny WR room last season. That and Hicks moving from TE to WR to provide depth and size. WR blocking should be much improved. The OL depth is better than it's been in a decade. All 5 starters return...Jurgens now has a yr of playing C under his belt after transitioning from TE. Jaimes is a really good T. Farniok is moving to his more natural position of G and Benhart, a highly recruited 4* massive T is moving into a starters role. Neb has landed a top 150 OL croot the past 3 cycles (Benhart, Corcran, Prochazka).
You can clearly look at the classes under Riley, Bo's last couple classes, and Frost's transition class and see where the lack of depth came from. Looking at Frost's 2019 and 2020 classes you can see a positive trend in building back depth while adding top 250 talent. Those guys are still young, but this season we'll see a lot more of them contributing.