Why do people complain about Vayne?
Edit: [Seeing how people are replying, "BUT WHEN YOU FEED HER, SHE'S OP AND TAKES NO SKILL". Think about that logic before you post for a second and use it as a reason for why Vayne is busted. Of course that occurs. That's literally what happens when you feed any champion in League. That's just common sense as to why you don't feed. Feed a Mundo and see what happens. Feed a Nasus and see what happens.]
She's pretty healthy as a champion to me. Her short range and her skill ceiling makes him unplayable to a vast majority of the community. She also is very easy to shut down due to her low sustainability like all ADCs. I even believe her range is equal to Teemo's and one stun will end her day.
Since she can only target one champion at a time, Riot gave her the ability to be a duelist. She's a ranged duelist who relies on critical chance and lifesteal to survive. 1v1'ing her(if the player is good) is a bad idea - especially if it's in the jungle where walls are just begging to be hit.
She does her job well and has her weaknesses. She has more weaknesses than most ADCs as she's more reliant on player mastery and reactions. She's (I'm using this lightly) adc version of Yasuo in terms of outplay potential.
Jinx and Twitch are much worse than this simply due to their AoE abilities. Twitch shreds teams all at once while Vayne does not. He sacrifices mobility and escapes with also high CD. Jinx has a lot of AoE(ultimate rocket and rockets[basic attacks]) with kiting prowess to keep her alive. I'm pretty sure once a good Jinx player gets a kill, assist, or tower objective - it's hammering time.
Most of the time, people forget teams protect their ADCs as they do a lot of damage or ADCs hide in the backline. This is simply called kiting and this is what people are complaining about Vayne on the boards.
She's a duelist and she's supposed to BE ABLE destroy you one-on-one. If you guys can't attack her at the same time, and just get hit with her silver bolts individually - then it just means you guys were uncoordinated.
Twitch's basic attacks each Poison icon poison his target with a Deadly Venom stack, dealing 6 / 12 / 18 / 24 / 30 true damage over 6 seconds, stacking up to 6 times for a maximum 36 / 72 / 108 / 144 / 180 true damage over the duration.