I use way too many addons and I'd kind of like to cut down, but they have a use that does improve the game.
Most I could live without, DBM for instance could be replaced by a raid leader calling orders, which I prefer actually over the dead silence of a raid.
Addons pointing out what transmog, rep, pets or mounts come from where are handy and should be default in the game. Ditto quest addons like Loremaster to FIND all the dang quests.
But I have no raid awareness so GTFO is one I do "need" though could live without by dying more.
The one I cannot live without though is Altoholic. If I had to go through every alt to find 30 tin ore I'm sure I mined a few weeks back so I can make some bronze transmog boots today, I would go nuts.
Even using guild bank alts who's job it is to store all my crafting crap and BoE transmog are useless if my tin ore is on an alt on a non sister server or the wrong faction.
Blizzard should have implemented much of this stuff years ago rather than telling us to go to WoWhead.
We might be the only game left that doesn't allow customization of body and face, but that's another topic.
The fact is, Blizzard has no competition so they don't feel much need to improve the game interface and stealing cool new things from other games is just plastering new yummy icing onto a stale cake.