Aside from not being mythological or a necromancer, what problem do you have with this description?

Describing Sauron as a 'necromancer' is akin to calling Gandalf a 'fireworks manufacturer'. It's a small part of their skillsets, and not what they've built their personal brand around.

I don't think there's really any evidence Sauron was a necromancer at all, so if you're going to explain these things to me, start with that. Sauron's army did not contain any undead. The nazgul are called "ringwraiths" but they don't seem to be any more undead than gollum or bilbo.

Tolkien wrote lord of the rings before the modern (silly) understanding of the word necromancer had been established, and sauron does't match that description let alone the more anthropologically accurate version (what today would be called a medium). Did sauron EVER commune with the dead?

Now Sauron was known as "the Necromancer", but that's a name, not a description. A serial killer known as "The Butcher" would not be a butcher (necessarily).

All we really know about Sauron is he was really good at making jewelry which had weird effects on people, that half his power was invested in "the ring" (which was also a ring), but his powers never really get displayed. He can make bad weather and mutate elves into orcs or something. But his awesome bad weather power was nullified by Gandalf, so that's not terribly impressive. And Saruman was better at making orcs than Sauron, so again not so impressive.

Actually, The Hobbit (that predates The Lord Of The Rings) firmly establishes Sauron as a necromancer (before we ever learn his name).

Read what I said. It establishes him as being referred to as "the necromancer", but he doesn't actually do anything necromantic. Ever.

There's really no evidence in Lord of the Rings that Sauron is a bad guy at all. The Nazgul smell bad and their horses are scary looking, but the only real war crimes we see are committed by the Riders of Rohan and Saruman. So, it's quite possible that Sauron was simply a victim of bad PR, much as we might refer to Sarah Palin as "The Moron" whereas she's merely of average intelligence.

There is quite a bit of circumstantial evidence against Sauron in Silmarillion. (E.g. the dwarf kings all meeting sticky ends, and of course the human kings becoming Nazgul -- but maybe that was because they wanted immortality and thought he was awesome. Which he kind of was. It's not like he went around telling people that dying of old age was a "gift".) But again, no necromancy that I can recall. (It's been a long time, and Silmarillion is mostly very, very boring.)

Sauron is exclusively referred to in The Hobbit as a "necromancer"; I see nothing wrong with this.

I think the original point was that he is not "mythical" but fictional. As for the necromancer part -- I've gone on waaaaay too long about that already.