Why does every mass update have to be a buff?

I recently started playing league again after a 4 month break (season 6 was just so horrible for me, though I feel like now it is at least playable, ty riot) But the thing i wanted to get into was the new assassin mass rework/update. Whenever these mass updates seem to happen, that balance is just absolutely terrible and horrible for 2-5 patches. In the long run, its worth it, because overall the game becomes much less toxic, but why does riot release these updates in the state they are in? The mage rework gave mages massive buffs the first few patches, the ADC rework/update made the game where there was an adc in every lane (that was fun...) and now this assassin update is looking like its giving MASSIVE buffs to assassins. Riot, just because you make something inherently less toxic (talon for instance, appears to have much more counterplay and be much less toxic) doesn't mean you have to give that champion a ridiculously large buff to compensate. toxic for the game does not always equal overpowered, so when you remove the toxicity from said champ, that doesn't always mean they are getting NERFED. You may help the game in the long run, but these changes are looking like the game is going to be busted the next few months, please don't make the same mistake you did with the ADC update.