That being said I do agree that there are huge differences in types of carbs consumed....but that only goes to say that the problem isn't simply 'carbs', it's processed sugars.
I have however met a lot of people who are Paleo or Carnivore who are in incredible shape.
I'm inclined to believe that at least some of this is cultural - Paleo/Carnivore folks tend to be more strict and disciplined about their fitness anyway, and do different workouts - and some of it is indeed due to diet.
I've only heard this idea from people who aren't in shape obsessing over all the details of the body except for the one that matters: having the discipline to exercise.
It's like debating whether you should have celery or its close cousin, rhubarb, while skipping your daily run.