The thing with drafting RBs is their careers are so short that you are basically getting them in their primes day 1. Thus resigning them to long term deals after their rookie deals is almost always a bad move (CMC, Todd Gurley etc) because they are usually on the tail end of their prime. I highly doubt CMC ever has a year like 2019 ever again... and the team still sucked!!
Drafting a RB in the first round makes sense if you are a contender (like how KC drafting CHE last year was a great pick) but if your team sucks then you're basically hoping for a quick rebuild.