At a high level, past say 10th level characters might encounter a flying ghost like foe. A mundane fighter that can't fly and has no magic at all can't do anything in this combat. So the player will just sit and do nothing. Many will say this is normal and acceptable and part of the game, while also saying they greatly dislike this. But as this is made into the rules, most feel nothing can be done.
At high level, say past 10th, characters might encounter an anti-magical glade with savage foes. The high magic spellcasters can't do anything in this combat. So the players will just sit and do nothing. Except here nearly everyone will be screaming that not only is this wrong, but it must never be done in a game.