Why does the most broken champion in the game always have to be an ADC?

I never see Riot let mages and most assassins ever sit at 53-54% winrates for patches let alone seasons. If Syndra or LeBlanc or Ryze or Azir or Zed ever had a 53-54% winrate they would be nerfed for like 3-4 patches back to back.

Meanwhile Twitch was allowed to sit at 53% for an entire year, Riot still hasn't directly nerfed Miss Fortune since early S7 lethality bullshit even though she has been at 51-52% all season and is now the most contested champion in the game after Ezreal. Ezreal didn't even get an actual nerf it was just a buff revert that was already excessive to begin with. We were told that Twitch would finally receive at least SOME change to his already unfair kit which never happened.