You can def build a great physique without AAS. Those guys are on steroids for the most part though. I personally think that what a lot of "natural" athletes are claiming to do is complete garbage. It was my experience as a competitor as well - not just using drugs can help edge out the competition, but the type and quantity of drugs can also be a large factor. It depends on what weight class you compete in and the level you are at, but plain and simple, some are completely inaccessible without drug-use.
The last natty comp I went to there were 6 competitors in one weight class which was at the heaviest middleweight (there only was one - it was some musclemania modeling contest or some shit). 4 guys looked good, 2 looked like shit. I knew one of the judges and afterwards was told 4 guys were red-flagged for steroids, 3 were tested, and 3 were disqualified. It is anecdotal evidence but it was what I was thinking before I heard those guys were on steroids: How the hell did those guys look that full without any drugs????
Man, if you look closesly, you can see some of those dudes in that video have face bloat. I doubt every kid in that video is on steroids since some looked very good but more practical - others just looked incredibly full and vascular. It all comes down to your standards - if you think "great" can be achieved at 6' and under 190lbs, then you probably won't need steroids to do it. What sucks is that there is no denying the fact that on any stage, at any weight class, with everything else being the same between two competitors, the guy on steroids will look better in a BBing competition (key point being everything else about them - size, symmetry, cuts, etc. - is the same before steroids are thrown into the mix). The added hormones inarguably let you hold on to more muscle mass as you get leaner. Try it with steroids, then try it without and you'll see. If one guy is on steroids and is of the same caliber as the other guys are in terms of being a competitor, he will probably win.
I would like to see a single picture of just one guy that looked like one of these guys in the 1920s (before sports enhancers were invented). There's a reason the BBer look is so new and only came about in the last 40 years or whatever is my opinion.