I think the conversation and debate on the value that RB's bring to NFL teams is a totally interesting and relevant conversation. "Is a team making a mistake by paying so-and-so this much money" or vice versa, 100% meaningful. But the whole "injustice" thing is just nonsense to me. If the teams are wrong in undervaluing the position, some teams will start to realize the trend is faulty, and start paying up again. If the teams are correct, then what's the issue? Should they have to pay more than a player is worth to them? Just because?
ETA: And like others have said, if the position isn't paying what you want, don't play that position. Granted, you don't necessarily see the trend coming in the 2020's when playing in high school in 2013. But that's life, just like choosing a business to start based on your assessment of where things are going.
It definitely sucks for the Barkleys and the Jacobs of the league, but really they're neither over- nor under-valued. There are 32 teams who set the market and this what the GMs and capologists of the league have determined what the value is for RBs. We're on the outside looking in as fans and we have a different opinion on the values.
As
@eighsse2 points out, GMs will start to adjust if they see value. Or when a team wins the SB on the back of a stud RB, everyone else will follow because its a copycat league.
And again, the issue isn't what the free market thinks of these players. The issue is that these players are blocked from being on the free market during the entire part of their career where the free market values them well.
If these guys were free agents when they were 23 or 24 they would be getting paid a lot more. Every other position still makes peak free market money at ages 26+, but for RBs the ship has sailed by the time they're allowed on the free market.
Again, this isn't something that was done intentionally and needs to be protected. It's not like they got together in the last CBA and thought "RBs really don't deserve to make good money during their few peak years, we need to set this up so RBs get overtly punished by this new CBA compared to other positions". It was an unforeseen effect of the CBA and hence, something that they can look to fix.