Quick side note, but I think this is a bit of a misinterpretation of the actual story as it was released (before TBC and Legion retcons).
TBC did ruin the Illidari, but not because they made them villains.
Play WC3 again. Illidan was a villain. All Warcraft material from 2003 to 2007 portrayed the Illidari as arcane-addicted, magic-obsessed anti-villain rebels.
That was their appeal. They weren’t good guys, nor were they pure evil. Hell, maybe ONE DAY they’ll stumble into an adventure that ends up saving us all, but they are not heroes. Illidan’s campaign focuses on him working for Kil’Jaeden to take down the Lich King. Illidan is more than willing to aid the Legion if it will ensure the survival of himself and his people.
But don’t just take my word for it. Here are some of Illidan’s lines from the game:
“HAHAHAHAHAHAHAHAHA…I have come to replace you. You’re a relic, Magtheridon. A ghost of a past age. The future is mine.”
It really doesn’t seem like morality is Illidan’s issue with Magtheridon. Seems more like he thinks he should rule in the Legion’s place.
“HEAR ME NOW, YOU TREMBLING MORTALS! I am your lord and master. Illidan reigns supreme!”
Does this sound…anything…like the guy we met in Legion?
Kael’thas and Akama were the only “good guys” in the group, but even then they only cared about their own people and their new allies.
There was no indication that the Illidari were these self-sacrificing anti-heroes with an edgy Jesus complex. I’ve been combing through old material lately, even stuff written in-part by Chris Metzhan, and everything we saw from WC3 to Vanilla portrayed Illidan as a “rogue demon” who wanted to be free from the Legion and study magic on his own terms. He even says the latter in Warcraft 3 cutscene.
“I never wanted mastery over this world. Only the magic!”
Remember, this was back when the Legion was portrayed as masters of Arcane magic (back when Fel and Arcane were two sides of the same coin). Going by Archimonde’s speech in Dalaran, they see the Arcane as something that belongs solely to them, and only those who serve them should be permitted to learn it.
So the Legion is an enemy of Illidan, but not out of any desire to save the universe from evil. It’s because Illidan is a rebel who wishes to serve no one.
Honestly, MoP did more to fix and expand upon Illidan than Legion did. From what I remember, the green fire questline revealed that Illidan was looking for ways to wean his demons off of Fel magic by replacing their “diet” with Arcane. Illidan was a sorcerer as much as he was a demon hunter, and he wanted to use magic freely and without corruption or restriction.
In short, The Illidari are a bunch of mutants and magic-addicts who were intent on mastering magic and freeing themselves from its corruption. They were ALWAYS villains, but not stupid and insane like they were portrayed in TBC. They also weren’t the cringey Hot Topic heroes we saw in Legion.
They were a unique idea for a faction that could only exist within the lore of Warcraft as it was known at the time. Now that arcane magic is no longer corrupting (or even related to fel magic) their old lore doesn’t really make any sense, so now they have nothing to do but be the self-righteous demon hunter faction.
Sigh. There was so much cool stuff in this franchise that Blizz has just gotten rid of…