I dismiss Necromancers because;
1. Blizzard stated that they incorporated the "ideas surrounding the Necromancer" into the Death Knight class.
2. The WC3 Necromancer's abilities were placed into the DK class.
3. Lichs, Ghouls, Frost Wyrms, Crypt lords, Abominations, Banshees, and other undead/necromantic units were also incorporated into the DK class.
4. The Ultimate Guide to WoW's definition of a Necromancer is exactly what the DK class does.
5. When Shadowlands rolled around
Blizzard increased the necromantic theme within the entire class.
6. No new Necromancer class in a Necromancer-based expansion focused on death and where every class gets a necromancer ability.
I fail to see how any of those arguments are bogus, especially when your counter to those arguments is pretty much "people are demanding it".