Scratching the surface and looking beyond the gross career receiving stats reveals that the old timers were just as capable as receivers as Faulk and Tomlinson. Brown, ****erson and Dorsett's abilities should not be dismissed simply because in today's NFL more play calls are made for screen passes to a back.
I think the problem with this argument is that numbers to not sufficiently describe ability, particularly for running backs catching the ball. Case in point, Jim Brown was probably by far the best player on those Browns teams. Why wouldn't they dump it off to him as much as possible? And considering how dominant he was at breaking tackles, dump-offs could easily account for 10 ypc.
In contrast, a guy like Faulk was able to line up in the slot (and split out wide) and actually find a way to get himself open. And not only that, but he had the body control to contort for tough catches, and he had the soft hands to be reliable. And then, after all that, he was still the great open field runner that was a threat to take it the distance.
I don't think it's even a fair comparison. Faulk would be much more useful in a modern offense that moves a running back around than Brown, who likely would have been limited to the backfield, much like other modern running backs (even great ones) who are sort of one-trick ponies such as Adrian Peterson.
Some of this goes back to what you actually value at any given position and how you would develop a scheme for this hypothetical team you are choosing one player or the other for. That's part of what is so fun about this exercise though.
Why assume that while everyone else was getting bigger, stronger and faster, the players we are talking about when hypothetically transporting them from one generation to the next would not also get bigger, stronger and faster? The same advances in training, nutrition, etc. would be available to the players from previous eras in this scenario. The expectation should be that those older era stars would still be bigger, stronger and faster than other players today.
That's one view to take. Another view is that the league has gotten bigger/stronger/faster, not because the same people who would have been stars yesterday simply train better now, but because *different* players have come into the fold that wouldn't have previously, either because there is more interest (football is more popular) or because their body perhaps is more malleable for training. And for the latter, maybe it's even a situation where the modern players would have been *worse* in previous eras, but now they are better in the current era, due to certain biomechanics specifics like certain body frames being less efficient until a high enough muscle mass is reached. Or maybe, modern training and nutrition simply has an equalizing effect: a naturally great athlete like Jim Brown remains a great athlete, but now the rest of the guys on the field catch up mostly and there is so much more competition for him to run against.
PS - Looking for anyone in the current NFL that could break my thesis, I found Leveon Bell, David Johnson, and Tevin Coleman as guys with some of the same skills that my smaller running backs that I previously mentioned also had. I'll still have to mull that over for a bit.
Of course, arguably the most talented of those three I just mentioned, Johnson, was not considered by Belichick either to be on Faulk's level as of last season:
Bill Belichick: David Johnson isn't Marshall Faulk
One of my main issues with taking someone who's one-dimensional like Adrian Peterson, not that he's not great nevertheless, as my best ever or 'prototype' is that nowadays, basically any top 10 defense can nearly eliminate the running game from the other team's gameplan, particularly if their offense can pass the ball well enough to force the other team to play from behind (and thus make running a less favorable option). If you have an elite running back who dominates as a receiver as well, you don't have as much surface area for a defense to do that to you.