Ok so pretend that over the past five seasons, Riot has slowly but surely been reducing the slot efficiency of adc items by removing ad and attack-speed and reducing the unique effects, but also reduced the price so it's over all not really a straight buff or nerf. This would naturally move the window of power for ADCs from late game to mid game, and eventually make them super strong at 1-2 items but fall off pretty hard shortly after that
So you only see like Lucian/Trinity EZ/Corki played, because while they have kinda shit scaling they have the base damages for a midgame spike. At the same time, assassins, a class given the base damages to excel in the midgame by default, are building adc items for the cheap damage spikes. Somehow this is the fault of ADCs.
So all the midgame ADCs are nerfed, and then all the items they buy to compensate for their weird scaling (lethality, tri-force, black cleaver, etc) are nerfed. This isn't super hard to believe, as it sorta actually happened.
So then in pre-season Riot says "ADCs are too strong in mid game" and takes 20-30% off the crit values off of IE/Essence reaver and Zeal items and "compensates" by buffing the attack speed/ad values by 5-10%. They also neuter the base defense stats of various ADCs that are succeeding, which are still the same ones despite the previous berfs because of course the others don't work. They rework the "struggling" ADCs and shove a ton of utility into their kits because they "Don't want them to just statcheck with damage".
And because adcs have been struggling to team fight, they also release an item that gives a ton of ad and attack speed, and has an active that doubles your crit in teamfight situations (when around enemies) but also amplifies damage against you by 60%.
And then it turns out that most ADCs are still performing on average a point shy of 50%, the ones that were arbitrarily overbuffed with utility are excelling, and historically late game adcs are unplayable because they just get sneezed on and die.
And everyone's like "This is fine, this is good, what are you taking about ADCs do tons of damage, look how much damage this adc did to me when I stood in it's effective range for 10s with it's team cc'ing me and with that item active, when they time their steroids properly and stay in exactly the right positioning ADCs can actually put out quite a lot of damage. Anyway, it's their job to die so that teamfights can begin, and it was unreasonable to expect them to do enough damage to actually threaten all 5 enemy team members."
"Adc mains are so entitled, they actually expect to be a damage threat to every opponent while also being able to take literally any damage from anyone without dying. Don't they know that tanks, with their sustained defenses and heavy cc are supposed to counter them anyway? I know ADCs do nothing but itemize damage, but tanks do nothing hut itemize defense. You counter tanks by kiting them and letting skirmishers and juggernauts them, not just hitting them over and over again. If you let tanks engage on your team you deserve to lose, it's so easy to avoid. Besides, you need an adc to consistently win, and their winrate spread is approximately across 50%. So what the hell are you complaining about anyway?"