These complaints were non existent on release two years ago, non existent a year ago, non existent a month ago. Where were you while people were complaining about darius, complaining about irelia, complaining about jayce? If it were a toxic kit we're talking about I'd rather talk about pantheon and vladimir. Riven gets all the flak while I'm not seeing that much complaints on taric who is legitimately much more infuriating right now.
First of all, yea, the complaints were very existent in the past, that's why Rivien was nerfed, more than once (hp/5 nerf and ulti CD nerf). So you start off by flat out misinformation. Also, those people could have been complaining as well, how do you know they weren't? And the argument "well there were other OP things in the past, so screw you" is not a very sound argument. And talking about Vlad toxicity, where he's in a very sorry state of being nerfed into the ground. Sure, his kit is toxic, but there's nothing to talk about as he's under performing anyway due to the numbers on his kit. Taric on the other hand does not have toxic kit, it's just simple to use and overtuned number-wise.
You know, Rivien is only in top 10 highest winrates over last month in diamond. Funny thing is, she's not in top 10 in plat, gold, silver or even bronze. So maybe you should stop judging if Rivien's OP or not if you mostly meet people that can't utilize her full potential?
Riven is not some kind of unbeatable god-like entity that has to be feared no matter what, but standing against her in lane allows for extremely small margin of error in most matchups, and even in equal ones, like Rivien vs Renekton (yea, Renek does not counters Rivien directly, his kit just allows him to win lane if he's better) you can loose heavily after minor slip.