Pretty much, what school do you feel is the most associated with pure magic?

I don't really know, a case could be made for all of them.

I think it's destruction and enchanting.

Destruction.

Neither, they all go together.

That.

Honestly, they all are.

In Skyrim I'd go with destruction because it's associated exclusively with harnessing the powers of nature - fire, lightning and frost. Isn't this what we imagine when we think of a mage's offensive abilities?

In other TES it's alteration, the school that deals with manipulating the world's natural properties. Levitating, water breathing, feather and burden, various shields - it literally defies the laws of physics.

Agreed. People often complain about pure destruction being a hard build, but IMO it makes sense. A warrior wouldn't walk into a battle with a weapon but no armor, so why would a mage walk in with destruction but no other school?

With Spellmaking gone, only Illusion offers the player opportunities to show any real ingenuity, so Illusion is the most "magey" school in Skyrim. [IMO of course]