The top fifteen that year might have been an outlier.
Fine. Let's go back one more season and expand the window to the Top 30 instead.
Top 30 RBs from 2021:
01 - Taylor (IND) - ADP RB5
02 - Ekeler (LAC) - Now with WAS. Current ADP RB31.
03 - Harris (PIT) - ADP RB24.
04 - Mixon (CIN) - Now with HOU. ADP RB15.
05 - Conner (ARI) - ADP RB21.
06 - Fournette (TBB) - Unsigned / free agent.
07 - Elliott (DAL) - ADP RB39.
08 - Gibson (WAS) - Now with NEP. ADP RB50.
09 - Kamara (NOS) - ADP RB16.
10 - Patterson (ATL) - Now with PIT. ADP RB108
11 - Jones (GBP) - Now with MIN. ADP RB18.
12 - Jacobs (LVR) - Now with GBP. Current ADP RB12.
13 - Chubb (CLE) - Currently rehabbing. Return date unknown. ADP RB35.
14 - Harris (NEP) - Retired.
15 - Swift (DET) - Now with CHI. ADP RB23.
16 - Cook (MIN) - Unsigned / free agent.
17 - Williams (DEN) - ADP RB30.
18 - Gordon (DEN) - Unsigned / free agent.
19 - Singletary (BUF) - Now with NYG. ADP RB34.
20 - Montgomery (CHI) - Now with DET. ADP RB19.
21 - Williams (KCC) - Unsigned / free agent.
22 - Henry (TEN) - Now with BAL. Current ADP RB8.
23 - Dillon (GBP) - ADP RB67.
24 - Robinson (JAC) - Now with NOS. ADP not in Top 114 RBs.
25 - Gaskin (MIA) - Now with MIN. ADP not in Top 114 RBs.
26 - Mitchell (SFO) - ADP RB58.
27 - Henderson (LAR) - Unsigned / free agent.
28 - Pollard (DAL) - Now with TEN. ADP RB29.
29 - Carter (NYJ) - Now with ARI. ADP RB105.
30 - Barkley (NYG) - Now with PHI. ADP RB6.
Updated summary: Only 9 guys are on the same team, only 4 guys are still considered Top 15 RBs, with 19 of them no longer ranked in the Top 25. The lifespan for RBs generally has getting shorter, there are fewer of them that stay relevant past 30 (now maybe even 28), and they still get dinged and miss time. Not sure there is much fantasy owners can do about that part. Fantasy teams still need to roll out RBs in their starting lineups, and you still need RB scoring to win. That doesn't necessarily mean RBs aren't good, it just means they can miss a lot of time.