The fighters are too professional now in a way. You won't see physiques like Tank Abbot or Roy Nelson come out of the new generation of MMA fighters. Ruins some of the underground appeal MMA had.
At no point have out of shape guys been a common sight at the highest level of MMA. Between Nelson and Cormier that's probably the most legit fat guys we've had in the top 10.
People always want to blame the thing(sport, games, hobby) when they lose interest in it. It's generally not the thing that changed, it's you. People change, there's no rule that you have to enjoy the same thing for your entire life. If you don't care about crazy exciting young champions like Jon Jones, Cain, or Aldo it's not because the sport is suddenly worse or less interesting. You've just had your fill of the sport, no shame in that.
There's a crazy level of young and exciting talent out there right now. The in ring action is as exciting as it's ever been. We just had a HEAVYWEIGHT contender win a fight with a spinning back kick. And the event before had another one. We've never seen fighters willing to take these kind of risks at the very highest level before, but now they are so good and so well trained they can go for it.
This guy...
Is going to be fighting this guy
(yeah, that's a double flying knee)
In August. Both guys are only 26.
If you seriously need bigger personalities to make you care you either need to broaden your view to non-contenders like Chael/Roy/Bisping etc, or you need to accept that you care more about storylines than the actual fighting.