basically free damage she can do to you from her team
Landing her E is far from free. Getting meaningful damage off of it even less so. It's one of the least free things in League...
Not to mention that Illaoi can 100-0 champs like Sejuani/Rammus through their spirits without ever touching them which is hugely beneficial right now.
What? How? That makes no sense.
She makes up for being the least reliable by having a far bigger threat range than other juggernauts, even Mordekaiser.
How so? Morde W out ranges her E and even if she lands E you can usually just walk away.
She doesn't need to bash her face into you to hurt you, and her range on Q and E means she can hit squishies through their front line.
What? She doesn't do much damage with a lone Q unless way ahead. Her E doesn't hit squishies through the front line at all.
her 2 second CD jump isn't sticky? Illaoi can be sticky if she wants to be.
It's only 2 seconds during ult. Even then it animation locks her a bit and is short ranged. By the time she's fighting someone besides top & jg they tend to be faster than her and any mobility spell or even just typical adc itemization will out run her despite W with ease.
Forcing you off of her means she can keep permapushing your side lane and making you spend more time trying to deal with her. As far as I'm concerned her overall objective control is the best of the juggernauts, and it's not even close.
That works for pushing a lane but it also makes her highly predictable and means she should never show up for dragon/baron. Unlike Trynd she's not good at tower diving or even that good at tower taking. If you try to gank her there with 3 or more people she can't leave and can't win or even trade unless ahead/they play like idiots. She is pretty good at the 1v2 in her tentacle nest though.