Jhin has a good toolkit but suffers from the fact he is very easy to get ontop of and kill, his reload time is also very punishing and a nuisance, unlike graves who can scale his reload with attack speed. His traps also have a laughable slow that arguably does nothing.
Illaoi suffers from how easy she is to counter play in top lane and in team fights, if she ults, you walk out of it, no problem, her ult is only effective if you can cc the team to stay inside it, personally I believe Jarvan + Illaoi can do some pretty insane wombo combos, and I look forward to seeing someone attempt it.
Suport Illaoi is also really good for lane bullying and is arguebly better then Illaoi top, but now you just lost a lot of cc, as your top laner mandatory has to play utility.