I mean, just look at the best champions based on their respective roles. We got zac, who hasn't been balanced since mid season 6 or maybe even before that. Cait, who has been ridiculous for a while now and countless good arguments have been made for nerfs. I'm not even sure how the hell ahri hasn't been addressed. I just got out of games against fiora and riven and laning against fiora is one of the most unfun experiences I've had all weak, but not nearly as bad as riven building black cleaver in randuins and two shotting me. I built armor pen and everything and she just doesn't take damage.
All these weird changes keep getting thrown around but you should really just nerf the problem and not try to change everything else. Cait was too strong so you buffed the other adcs. 1/3 of the junglers had too much pressure so you change the entire jungle and left a lot of the junglers almost unplayable. adcs weren't strong enough so you lower the price on all the crit items and make yasuo and tryndamere stronger.
Basically everytime riot tries to fix a problem, they either make it worse or create an entirely new set of issues. The only reason it keeps happening is because they keep trying to do these huge role changes when all they need to do is focus on one problem at a time.