Why don't the Dunmer worship the Aedra? It seems (in MW) that they have no relationship with each other whatsoever, even historically.

You almost answered your own question: they have no relationship with each other their whole history.

Remember that Veloth led the Chimer/Dunmer Exodus from the Altmer tribes to complete the Endeavor, part of which required that they discard Altmer traditions (that included worshipping the Aedra).

So they just give up on a whole pantheon of gods because they want to differentiate themselves from the altmer?

It says something about the divines if they lose followers on the whim of people reinventing themselves.

Edit: And that the Dunmer have had no interest in reestablishing any sort of relationship.

It's a bit like asking why Crhristians are christians and why Muslims are Muslims, in my opinion....

The Oblivion Crisis, the death of the Tribunal and the ascension of Helseth to power, may have changed that.

I believe they abandoned Aedra worship when Boethiah supposedly exposed Trinimac and the Aedra as liars.

Well, Vivec speculates Dunmer religion will shift back to pre-Tribunal ancestral worship.

I probably shouldv'e asked WHY the Dunmer think that the Aedra have nothing to offer.

The other way round.

They gave up on ze Aedra and then were forced to differentiate themselves from the Altmer.

Think of it like the Reformation on Earth. Or the creation of Christianity. Or a lot of religions.

Because the aedra always whined over the creation of Mundus and how Lorkhan "tricked" them, and not realizing the point of creating the world(s). Boethiah basically demonstrated to the Velothi how Trinimac and company were just a bunch of whiny little *****es.

I forget his exact words, but he implied the Temple would revert to worship of ancestors as well as the Good Daedra, and the Tribunal would be seen as saints and heroes of the people, nothing more.

Hence why they have such bad things to say about the Imperial Cult's Aedra, because they don't know that they're mythologically different.

Also, it sounds like an example of Daedra drawing away followers from the Aedra. Boethiah, Mephala, Azura, Sheogorath, and Malacath seem to have a particular fondness for mortal followers.