most of them do.Most of them can't, though. The vast majority can't. And it's okay that the fighter has trouble with some, just like the wizard doesn't really do well against creatures that have advantage on saves and resistance to magic damage.
Most monsters CR 11s in the MM have strong range attacks, spellcasting, invisibility, teleportation, or flight. A few have multiple of them.
Fliers, teleporters, invisbles, shooters, and casters are extremely difficult to handle in combat for noncasters if they don't have countermagic in items.
Therefore the majority of monsters require certain types of magic items for the fighter to battle them well.
If D&D fns don't want this they need more Goristos and fewer Dragons and Liches.