Can you make a great rpg even if characters do not have inventories?

[Norfleet]

That's still an inventory, just a highly simulationist one. In fact, I've heard that CDDA actually simulates pockets and other containers.

Well, at the very extreme, where the player never possesses any discretionary objects at all, not even things like "ammo", it'd be an RPG where the player goes through the game without ever changing his weapon, if he even uses a weapon, and the weapon would have to be a melee weapon or his bare hands, so as not to have ammo. Itemization of any kind would essentially be entirely stripped from the game. Still doable. Itemization is probably one of the more boring aspects of the genre anyway. You'd essentially play as a guy whose weapon or lack thereof is determined at character creation or is fixed entirely, and if he ever gets an upgrade, it's non-discretionary and handed out as a part of plot progression rather than by itemization. There'd be no potions or other consumables, and the only interaction with "items" would purely be non-discretionary plot tokens like quest MacGuffins and keys. It could work: Most itemization is fake choices anyway, given the existence of "best in slot".