I do agree with this, and this is part of why I've chosen to focus more on marathons and halves over the past couple years. With the marathon, even an extremely fast vs an extremely slow course will only be a difference of, what, 10 minutes? St George is one of the fastest, and unless we're counting that one road marathon that goes something like 5000' up a mountain, most typical courses are within 2-5 minutes of St George (2 for Dubai or Berlin, 4 or 5 for more typical ones), with really slow courses being maybe 10 minutes slower. I'd like to do another 100 again, but I don't see the reason to do it on shitty trails full of sharp plants that cut up your legs or in heat that makes you vomit. If I do it, I want to see what time I can run if the stunt elements are removed. I'll probably still suck at it, but it'd be nice to see what I can do. That said, I do see why Hardrock appeals to people. That course is incredibly beautiful and I've yet to see photos from any other race that come even close to comparing to Hardrock. I don't have much interest in doing it, but I'd thoroughly enjoy getting up a peak or two on the course. The people doing Hardrock seem to do it more for the scenery than anything, and I respect that. It's not really about stunts for them... I think, more than anything, they want to link up some really cool terrain in Colorado.
One thing I've learned is this: finishing an ultra isn't a big deal. Gutting out a finish on an injury isn't "tough"; it's stupid. Running a marathon at your maximum capacity is vastly more difficult and painful than finishing a 100 miler on average 100 mile race terrain. No doubt, I had to dig deep in 3 of the 4 100 milers I've finished, but I had to dig much deeper to run my marathon PR.
Finishing a 100 miler is not something particularly special after the first time, and not something that people should make a big deal out of, which is why I'm not really interested in running media circus events like Western States. If I get back out for another trail 100, it'll either be Old Dominion or Wasatch. Old Dominion because it's a special, historic race with literally no real finish line and no fanfare. You do the race, 1 guy takes down your time, and you go to bed. The cutoff isn't overly easy like most 100s, and they don't give you a buckle for finishing in 35 hours. I like this. You actually have to be in halfway decent shape and not slack off for the entire race if you want a buckle. Wasatch would be because it's still very low-key, but more than anything, because it's on my home turf, and through places that I thoroughly enjoy running. That said, I imagine my next time would be on a road course just to remove all of the stunt elements, which really grew to irritate me in my time running ultras. For now, though, the 50k at Speedgoat (more than anything, because I love skiing at Snowbird) is the longest race that appeals a lot to me.