You cannot say bodybuilding has "regressed" quite the opposite is true. Guys are bigger and leaner than ever before.
The problem I think comes down to one big thing- bodybuilding is dead in terms of mainstream appeal and profitability for the athletes. What this means is that the genetic pool of up and comers and guys who want to get into the sport is dwindling. Guys with the best genetics are playing other sports. For the most part no one wants to be a bodybuilder except a small group like the Ronnie Colemans, Jay Cutlers etc (who could have excelled at other sports), your homo types like Will Harris and Kai Green and here and there your genetic oddity's who do very little and achieve a lot (Wolf jumps to mind).
I mean overall this whole debate over mass vs aesthetics and what have you does come down to genetics by and large. The reason why so many top guys look like shit is because they are not that great genetically and are super huge because they are mega responders to GH and Slin. That pretty much sums it up. They don't need to train hard, just pump more and more drugs and stand onstage at 250 260 270 and collect a check. But you can see right away when you look at them that the look is not good. It's just an odd look, I cannot put it into words.
The bottom line is that as long as there is no money or fame to be had, 9/10 guys with great genetics aren't going to do it and thus you are left with an inferior gene pool. The guys who do make it aren't going to look nearly as good as the 70's 80's and 90's there is no way around it. The Bob Paris type guys, the Shawn Rays, Kevin Levrones, guys who looked fantastic without 36 IU's of GH are playing basketball, baseball, boxing, MMA etc. Everyone cites the same group of bodybuilders as being "the best ever" and not having "the bloated mess" look and for good reason- they were genetically superior and did not need mega doses to get huge and ripped. They naturally had wide shoulders small waist, great arms and back etc. The drugs simply took great genes and multiplied with great training produced amazing physiques.
I could go on but that is the gist of it. Phil Heath has damn near no competition right now because he is a genetic elite. He should be competing against the Shawn Rays, Kevin Levrones and Lee Haney's of today BUT THERE AREN'T ANY! But he is a great example of how shallow the gene pool is now. His genetics aren't the best ever, they are up there for sure, but there should be at least 8-9 guys who have similarly great genetics that he could battle it out with and there isn't. So we the fans of the sport sit around bitching about the good ol days because it's the fucking truth. Bodybuilding today ain't what it used to be.