If I recall correctly there were three reasons given by Riot. None of which made sense.
The first is that "They wanted a champion who used magic in a physical way."
By my recollection, however, getting your soul ripped out and getting hit by etherial tentacles isn't exactly a physical process. Like, at all.
And if you wanted a champion that mixed the physical and the magical almost as if a hybrid...... Why not make her hybrid?
The second was they didn't want to add autoattack modifiers to make her autoattacks feel useful. But then.... Considering that , without CDR, her Q is on a six second cooldown and her W is on a four second cooldown, why does she need to be using autoattacks?
Is there any reason for her to be autoattacking outside of the fact that her W is technically an autoattack?
I can't see a single reason with her kit why she would ever need to boost her autoattack damage. Especially considering that passive.
And the third was that, as she was being developed in tandem with the juggernaut update, they wanted to align her with that.
Which strikes me as particularly eggregious. Considering that juggernauts are champions who are defined
A) By their melee nature.
B) By their lack of mobility.
Illaoi happens to have both an eight hundred range harassment tool and a four second cooldown gapcloser. Bruiser?
Something akin to Garen/Skarner/Morde/Darius?
Plus that isn't even a reason. So you wanted to make her a tanky damage dealer?
Morde seems to pull that off perfectly well with hybrid scaling.
Why couldn't Illaoi?
Did you fear that, if given the option to build AP, she wouldn't look first and foremost to the new bruiser items you were pushing or something?
'Cause if so, that's an absolute crap reason.
You should make champions with the stats that they'd work best with. If they're ability focused and have absolutely no reason to be autoattacking at length, m'thinks you shouldn't be making them AD.
But you have a history of doing that.
The question first and foremost is why is Illaoi AD. But beyond that, why are so many champions who have absolutely no business being AD entirely AD?
From what I can tell it has caused nothing but problems to make them that way.