I'm not sure if you have seen a kid with genuine bad ADHD then. Absolutely nothing will hold their attention.
The opposite, but it doesn't mean the attention is held.
> ...or are these just difficult kids to manage in a room full of kids...?
If you remove "just", "to", and "of kids" then yes.
People—kids and adults—with severe ADHD struggle to manage in all sorts of rooms that others struggle dramatically less in, if they're undiagnosed and have no resources for dealing with it.
If you look back through history, you don't suppose you might find a pattern of people saying, "Kids these days," do you?