Fair enough, and I respect asking for a courteous answer.
Overall in the league the movement has been to more of a passing game.This is the common trend the league is going, but it requires a dominating passing QB, and there are maybe six of them in the league. If you are not so blessed, you make schemes that make it easier. One way is the spread offense, which we saw make Fitz look like a long term starter for a while with barrel scraping receivers. Other examples are the Chip Kelly system.
Greg Roman's (it's arguable how much of it is his how how much is Harbaugh's) revitalized the deemed bust Alex Smith, and plugged in a 2nd round pick that few had heard of to superstar status by forcing teams to send 8 or 9 men into the box to contain a power run game, leading receivers to be free in 1 on 1 matchups. If you have talented guys like Sammy and Woods (and hopefully an easy dump off TE who can fight off a safety and get 5-10 yards after the catch consistently), you tend to win those matchups. But you still need to run the ball effectively when you have those mismatches with 8 or 9 men in the box.
Good fullbacks, really good fullbacks, when used in creative systems can help a ton. They can not only grind out hard short yardage situations, but they tend to be used in the screen game, and most importantly clear blocks for the superstar speedster running backs. In unglamorous work, and it tends to not get you big paychecks, but if you don't want the RB you are spending $8M a year for to get clobbered, and hit the hole for big yards. If you set up them as primary blockers, you can also fool some teams when they are the main ball carriers to get reliable yardage.
Felton is considered one of the best in the game, and Vikings fans I've heard from say that he was a big component to AP getting his 2,000 yard season.