I’d respect your opinion if you weren’t wrong.
Undercity is useful for farming material, leveling and using the totems. I got my first mystic unique Helm of Perdition in the Undercity for my Necro first time using one.
Citadel was basically a test run as a team based raid. It’s good for passing the time and used it to farm the cosmetic Khazra set. That’s what it’s use was. I expect there will be more items that you won’t be able to farm anywhere else in the future.