Fine, but if the most effective back gets the most carries and is very successful, do you think he'll play for a much lesser salary than Zeke, if he even stays on the Cowboys? Or will you have to pay him the $13 million or more, or let some other team pay him? So you'll likely have the same Zeke situation again. Or you can get two more young backs and get them in sync with the offense.
And running back by committee doesn't work that well, looking at the latest SB for instance, the 49ers used 3 different rushers, who had 12, 5 and 3 rushes. KC had one with 17 and one with 1. Who won? Chiefs.
SB 2018, Pats had one back with 18 rushes and one with 7, Rams 10 and 7. Pats won.
SB 2017, both teams had carries split fairly evenly, butit was a weird game with the big comeback by the Pats, so that game is somewhat an aberration.
SB 2016, Broncos had 23 carries by Anderson and 5 by Hillman, Panthers had 3 backs with 12, 4 and 5 carries.
It' still true, if you have the "bell cow" back who gets most of the carries, that team tends to be the most successful....