As LS put it, kha is a champ that punishes bad players more then good ones, he is the "isolation" champion, which in higher elo basically translates to "misposition and die" champ.
Since his R got switched back, they kinda hurt his effectiveness.
What I DO NOT agree with though is the double ratio on his passive, that IMO was too much... kha'zix should actually steer away from more damage on his passive and be given more to his unisolated Q or his W for efficency in all elos. Buffing his passive makes his one shot auto attack in his duskblade+dark harvest even more appualing and as a kha main, that's not the version of kha'zix i find fair to play or play against, Q with E resets for play making is fine with R outplaying, autos that do it all doesn't offer much counterplay or room to flex his skill.
I was fine with the W buff and thought people were just being dumb complaining about kha getting buffed, but I can see a bit of ranting regarding the passive buff, not just because "kha is being buffed" thats stupid, but because that's not the direction kha'zix should be going.
Also
https://youtu.be/Dc7vh1k9Tak?t=526
This is why kench was changed lol. people shouldn't put all the blame on riot when tahm players (LS calls tahm his son) threw this idea in on twitter.