I think home-field advantage is most evident when teams are lacking in confidence. One or two good plays that bring the fans to their feet can inspire players, which can lead to greater effort, which can lead to more good plays, that can lead to the crowd going wild, which can...
In other words, at home there is a greater chance of getting a positive response that will lead to more effort.
But the best teams, the teams with confidence and that buring competitive drive, don't seem to need that - they actually relish going into a hostile environment and taking the crowd out of it. I think that's what's lacking in the players - there aren't enough that have the buring competitive drive to want to impose their will on the crowd.
Generally speaking, though, that's a trait you can't coach into a player - the player was born with it or developed it himself long before he came to college. While it can be argued that Incognito ultimately harmed the team more than he helped, I don't think any one would argue that he was one of those people that wanted to dominate - one of those guys that loved nothing more than to go into an opposing teams stadium, and hear the crowd grow silent.
That, to me, is what's lacking in this team.