You do realize that a single event doesn't indicate a trend? Especially with all of the unknowns surrounding Vitor's past. Overwhelmingly so, fighters today are better than they were then. This will likely always be the case (modern mma > past mma, in terms of skill).
It is also a fact that Vitor is more skilled today than he was back then.
well he was juicing on his way to the title shot too. and he's been training all these years improving his overall skillset with top camps. would you seriously argue fighters aren't better as a whole now?
It is clear that he has always used PED's, probably more in his 20's given his WWE body back then, so that factors out when comparing him in 2005 to him in 2013. Sure he has improved his skills over time, and guys know more now than they did back then as there are more fights to watch and learn from, but my point was that I think the whole "fighters are so much more skilled now" thing is overblown. Vitor knocked Luke out with a spinning back kick in 2013, but Chuck landed a big spinning back kick to the body on Vitor in 2002; the techniques were always there, outside of the Pettis off of the cage thing of course.
I think the biggest difference now is that a lot of fighters grew up honing their styles to win under the unified rules, where 10-15 years ago, the unified rules were new, and guys were fighting in different promotions where the rules were different from promotion to promotion. So guys focused more on finishing fights because that was a clear way to win a fight no matter where you were fighting. Not to mention that fighting that way was going to get you invited back, and fighting like Cruz was going to get you booed out of the building.
So to answer your questions, yeah, I think there is a level of professionalism that exists now in terms of well roundedness, preparation (nutrition, conditioning), gameplanning, etc., but I think the idea that there have been these exponential leaps is silly.