They own those specific expressions of them. The barbarian that rages, the cleric that turns undead, the druid that wild shapes, the rogue with uncanny dodge, etc.
They really don't.
WoW's Druid, for example, does literally everything a D&D Druid does (in broad terms), particularly the Wildshaping. As others have said, holy men "turning undead" is mythological and not specific to D&D. Berserkers are well-recorded throughout history. WotC could probably argue a claim on some of the wackier Barbarian subclasses, but the more "normal" they are, the more "on-brand", the less they could. Men who are sneaky, pick locks, and dodge attacks have been staples of fiction for like 150 years? More?
I can go on. Warlocks - fit historical portrayal of witches/warlocks and are even predated by some kinda-similar classes like Dark Age of Camelot's Warlock (they also have a pact, but with a specific named being). And fantasy fiction is full of dudes will ill-advised bargains with beings of great power.
Wizards? Vancian casting is nicked though maaaaaaaaaaybe WotC could try to claim they own the whole spell slot thing? I'd kind of love it if they won that and everyone just stopped using bloody Vancian magic to be honest.
Bards. Hahaha no. There are a million Bard classes in countless games who combine song, spellcasting, and maybe some degree or melee or ranged aptitude.
Paladins. It'd be way too dangerous to try and claim this because too many Big Boy videogame companies use Paladins and call them Paladins, even if the historical inspiration angle is limited. You want to mess with Activision-Blizzard and Microsoft? I mean come on. Sony too.
I mean, I guess you get the point. At best WotC might be able to put a rope around some subclasses and the names of things.
