These debates are what happens when you try to assign an individual award to a team game. Opinions will certainly vary, but I don't think the voters have been that off base over the years. The point of the game is for your team to win, so winning should be a huge portion of the MVP recipe or DNA.
As for some of the things being bandied about, many of the supposed negatives that are being used to detract from some of the candidates have nothing at all to due with the candidates themselves.
For example, running game, defense, schedule, injuries, coaching, OL strength, play calling, system, scheme, etc. have NOTHING to do with the QB. Is it Tom Brady's fault his team allowed the fewest points this year? Isn't that what teams are supposed to try to do?
As has been said many times over in this thread, it's a team game. Some comments in here would suggest that candidates from (potentially) inferior teams should win the MVP seemingly every year and penalize the teams that have all the attributes I just listed. Sticking with the Brady theme, is it his fault BB is his head coach? Is that part of the new appendix to the voting . . . candidates cannot come from the team with the best coach.
I would also suggest that the offense's impact on the defense is greater than zero. Score a lot of points and the defense doesn't have to worry as much. Don't give a steady stream of giveaways to the opposition in your own red zone and your defense will give up fewer points. Hold on to the ball and play keep away, the defense gets more rest and has fewer plays to defend.
In this scenario, I think there are times where having a pass heavy team could actually hurt the defense. Throw three quick incompletions and your defense is right back on the field. A more balanced offense might help keep the offense on the field . . . but it could hurt the QB's passing totals by 1) losing out production to RB's, 2) running fewer plays by keeping the clock moving, and 3) give the impression that the QB wasn't doing much to win (see, Bell, Le'Veon as EXHIBIT A in the game against MIA where he literally had every yard in one of the Steelers' drives).
The players are locked into their teams and whatever good or bad that entails. Tom Brady has to play with mostly non-descript receivers with Gronk being hurt, but in return he gets the Pats defense and BB. Rodgers has to suffer from having no running game and no defense, so he in turn can benefit from having no running game and no defense. Ryan gets to benefit from playing 9 games in a dome and putting up video game scoring totals, but then has to take the crap people will fling at him because his team won easier than some of the others.
Rodgers can be lauded for winning 6 games in a row down the stretch. Roethlisberger was in a similar do or die situation for the most part, and the Steelers won 6 down the stretch to get in the playoffs. I guess Rodgers winning his 6 games by 11 points per game was that much more impressive than Big Ben only winning his 6 games by 10 ppg. And I guess Rodgers winning streak trumps Brady's 7 game streak to end the season with a 16 point margin of victory. I get it. Rodgers had more style points and Brady should be eliminated because he his TD to INT was only 16-1 down the stretch compared to Rodgers 15-0 TD to INT ratio over his last 6 games to get to the playoffs.
When the baseline or expected level of performance is set so high, doing great things becomes the norm. This was the 6th time Brady won his last 6 games like Rodgers did. One other time his TD to INT ratio in his final 6 games was 17-0, and clearly 17-0 in 2010 was better than 16-1 like it was this year.
Most years there will be a lot of players with hot streaks, teams that go on good runs to make the playoffs, RBs with crazy numbers (did anyone even bring up DJohnson's 15 games in a row with 100+ yfs?), or as Seinfeld would say unbelievable feats of strength. Not sure why Ryan beating the Rams and 49ers down the stretch by 4 TD in each game is a net negative (it's the system . . . it's the running game . . . it's Julio F'ing Jones, man!) Yet Rodgers gets more props for beating the Bears by 3 points and only scoring 30. And the Falcons beat the Packers this year on top of it.
Six of the Packers 10 wins were one possession wins. Six of the Falcons wins were by 14 points or more. But that's just another example of why RODGERS is the one that's more valuable.
To bring things full circle, every year there will by segmented stats, opinions on talent of teammates, breakdowns of numbers to the nth degree to make a case to pimp up a guy. So many players can make a case for being MVP. IMO, that's why the voters look at wins as a barometer. It's hard to argue against which teams won more. It's right there in black and white.