But some people play them with just a Dance pad. Doesn’t that, by your logic, mean they are too easy? Shouldn’t they be even harder? Maybe they’d be even more famous. The point is that difficulty is relative, therefore there OBJECTIVELY isn’t a correct difficulty. You’re just lucky enough to fit into their “difficulty demographic”.
But it’s moot anyway. Games with easy modes will still get played with high difficulty by people that actually enjoy it. Your own enjoyment of a game should not depend on other peoples difficulty levels.