You haven't been playing long or haven't been listening to Riot long if you think this hasn't grown worse with time.
Most complaints stem from a growing and increasing problem. And Riot's treatment of it, does deserve the hostility.
You can white knight if you want, but when you have a hundred people who do the math, play on your pbe and TELL YOU something is going to ruin a character, and worse, isn't fun to play? And you tell them "Well sucks to be you, we don't give a f-" Yea, you deserve the hostility. This has happened for a lot of reworks now. Karma was somewhat half and half. Veigar it's been the same two people defending it, usually on smurfs. Same for Cass, same for Skarner. And what happened to the playrate on all these characters? Either they ended up solid and were nerfed to being almost never played. Or they were unplayable, as expected and buffed until their numbers meant they had to be good. But none of them were fun to play.(Well, with the exclusion of Veigar since he hasn't been released just yet).
So all these immobile zero dash characters got a bunch of flaws and dependencies. What about the Kass, Katarina Rework, and mobile character reworks? What about Leblanc? None of them were made entirely dependent on skill shots. None of them have real flaws except two of them being melee. Leblanc has a skill shot that should be hit, but when you can blink in point blank its pretty hard to miss anyway.
But who isn't nerfed into oblivion or made miserable to play? The same flashy playmaking characters.
Supports, who is nerfed? Traditional supports that counter Blitz/Leona Thresh who are the most played, and Blitz Leona were barely .7% below Sona in win ratio? Who gets nerfed? Sona, for "Being unhealthy for statistics we can't show you". I want to see these "unfun to play against" stats cause I think getting tower dove by Leona 15 times in a row gets old personally.
Basically? It's become very clear they cater to esports more then the community because their "balancing" makes older, less played characters more unenjoyable, not more fun or more balanced or any bs like that.
Niche picks shouldn't be played anymore because you WILL get screwed inevitably.
And yea, I use to adore riot, but the past two years were not the same as my first 2.
If you can't see the favoritism, then you won't ever see why so many people are pissed at Riot.
Edit: to tack on something. Being a professional balancer shouldn't mean that you ignore feedback that makes the game unenjoyable. Tank junglers, immobile mages and traditional supports have been getting screwed more and more over the years. And Riot's attempts to "fix" it have made it worse. So yea, you can all us out, but after two years I think I have the right to lose faith when a lot of board predictions come true.