ADCs are strong, traditional marksman (as/crit scaling pure AA based carries) are weak. Ye most of them average out at 50%, that does not make them strong.
You need context behind your statements, as an adc main I average a high winrate at the good ol' adcs (not the spell carries), but that is because I know when to pick them and I can only pick them during a game at which a Jinx/Trist/vayne etc.. can work. The strong ADCs are those that you can blind pick and will always work. Lucian/Ez/Sivir has fewer weaknesses in the current meta and can easily be blindpicked in almost every game.
As an old Jinx main I hate this meta, because I can't play her. The TP/Dive meta really hurts some certain carries and that's why there is a lot of adcs asking for buffs (or nerfs for others) certain ADCs. Jinx has not been viable for about half a season, Trist had a spark of light before rageblade was reworked, Vayne has been garbage for a while (not sure atm though, new items might make her strong again). Ashe abused rageblade just as Trist but has a decent mid-game with her ult and that is always good in soloQ. Twitch is an assassin mid-game to carry him to the late.
Kalista was hit hard by the nerfs, Corki has been nerfed after his dominance in midlane... urgot is urgot...
You need to use some context with your winrates, because when you dig deeper. The strongest ADC atm is Lucian, sivir/twitch/ez are following him, depends a lot on the teams for them to shine though. Caitlyn is also good atm, her siege power is absurd.
edit: I haven't mentioned some adcs, such as Draven/Varus are pocket picks that I haven't played enough to comment on, Jhin is a good counter pick with great laning, he's quite bad against the top tank engage meta so he's not as strong atm.