That isn't quite true. The rules have helped the passing games, which has in turned helped the offenses because the NFL does want more points. However, these same rules have aided the rushing game as well. It's a lot easier to run against 7 in the box as opposed to 8 and often defenses are even more spread out than that. Defenses have to focus more on the pass because just about every team can do it. The steady increase of league-wide Comp% and TD-Int Ratio, plus our naked eye can attest to this.
At the same time, league wide yards per rushing attempt has also been trending up. Going back to '08, league y/a has been either 4.2 or 4.3 every year, 6 straight years. Btw, 2011 & '12 are the only years it has ever been as high as 4.3. It was 4.1 in '07 and 4.2 in '06, making it 7 of 8 years of at least 4.2. Go back to 2000. League y/a was 4.1 that year and has been at least that high every year since except for '05 when it was 4.0. Now think about this, from 1999 back to the beginning of time, 1932 in this case, league average has only been as high as 4.1 15 times. A six year stretch from 1958 to '63 accounts for 40% of these with the rest spread out once or twice a decade. Most seasons the average was 3.9 or 4.0. Just in the 90s, it 3.9 or lower in six of ten years.
I know, a tenth or two-tenths of a yard doesn't sound like much, but it is a sign that the running game has not been restricted in any way, shape or form. A little less utilized, for sure, but not restricted.
As far as the actual discussion, I do think another RB will win MVP, whether one busts out for 2000 yards rushing or 2400 yards from scrimmage (rushing & receiving) with a bunch of TDs. It just has to happen in the same year when some QB doesn't throw a gazillion more TD passes than anyone else.