That's a huge exaggeration, Kat would never one shot with just E+W, she'd throw a multicasted Q with E in there. How fast you could press your buttons? Doesn't that apply to every champion in the game though?
New Kat can't burst someone that fast anymore? Ah, is that why people are dying to one dagger+Gunblade+Shunpo? You're right, with proper positioning no Kat player will win lane, yet you forget this is League of Legends, a game known for its autism.
More people do complain about her now, hence why if people say she's absolutely busted. She was only an annoyance to people pre-rework, now they view her as a "scum-fuck" champion.
Look, I main Kat, and I've done so for 7 years now, never have I actually encountered anyone who has said that pre-rework Kat was broken, because let's be real here, she wasn't. She was situationally good but that's about it. She lost lane to pretty much everyone, which gave her a clear weak point in the game and she only really steamrolled if her opponents didn't know what she did.
Furthermore, the rework turned her more into this AP version of Riven. As such she's hardly an assassin anymore as much as she is a mobile skirmisher.