it was bound to happen, because of all the rule changes. The league decided a few years back, that more scoring is needed, to bring in more fans. scoring generates excitement and even the casual fans who may not understand football, can participate and celebrate. its all about more money. its all about growing the pie. That may sound negative, but its not intended to. so with more scoring as a goal, the league became more pass friendly. more passing, faster pace, more exciting plays and more scoring, thus the running game became devalued and QBs values went through the roof.
further, teams realized that they don't need a star RB and pay him loads of money (haven't we experienced that). They realized that a RB by committee works (see Philly, chicago, Ravens, Dallas) and actually works better, because you can have a pass catching RB, which adds to your passing game. With more RBs coming out of college from spread offenses, with more QBs coming from option offenses and their ability to run, the RB further became a devalued position. Given the cap, QBS values going through the roof, then something had to give and that was the RB position. I don't think we will ever see another Emmitt Smith, as RBs also have a shorter lifespan in the NFL, as we have seen with Zeke, Cook, etc. and we have also learned its one of the easiest positions in the NFL to replace. you can actually have a rookie who can have huge impact on the team. have that player for 4-5 years and move and draft another one. its one way of managing the cap.
so not surprised to see the RB position being devalued as the game evolves. we saw FB position disappear. we probably won't see the RB position disappear, but doubt if we see most of them get large second contracts.