The problem with ADC from someone who plays a lot of ADC
Basically ADCs are very polarizing because there is a best case scenario and a non best case scenario
Best Case: You have a coordinated team with a balanced team comp, your team is even or ahead, you have a support reacting well to enemy engage and disrupting and protecting you with their abilities, you've been allowed to farm, get your items and hit your power spikes.
Worst case: Your team comp is a clownfiesta, your support is autofilled and they instalocked first time Brand with Doran's Ring and Ignite, your top and mid are doing well but bot is getting camped due to no wards, you're underfarmed for teamfights and the most you can do is plink their tank or bruiser for 80 damage an auto and the game is already decided before you get to late game.
Riot pushed down ADC build costs to make scenarios trending towards "Worst Case" more bearable, but that means ones trending towards "Best Case" become frustrating if your job is to kill the ADC because they become more powerful earlier.
What's the solution? It's actually obvious but Riot is absolutely against it and is actually moving in the opposite direction: longer games. If I pick Vayne or Trist or Kog, I want the option to play for late game. But guess what, that option doesn't exist because if I pick Kog, unless the enemy team ints me kills we'll lose even fights because I don't come online for 10 mins. And because having HOTS like objectives in a game not designed for it was a BAD IDEA, losing fights for objectives means the game ends before I come online. Other than that, I don't know. Especially since you have to have some kind of physical DPS we can't have strong melee carries because they get whined about and nerfed into the ground
so no matter how frustrating ADC gets to play they'll still be played.