An adc that is ahead has 0 counterplay and is the most unfun thing in the game

I'd rather play against a fed caitlyn than a fed olaf...

You gave no reasoning as to what makes them unfun to play against, and saying that there is no counter play is one of the stupidest things I have seen. Exhaust, Stun, Snare, Frozen Heart, Thornmail All of those destroy adc's and if you don't have any of those on your team than you all made a terrible decision.

How do they have 0 counterplay? They get hit by any decent CC and your team can blow them up in a couple seconds. There are far more annoying things to have ahead in an game than a ranged AD.

A fed ADC has counterplay. They only have lots of dps and probably nothing else. If you can catch them where they don't expect it and cc them, your team can likely burst them down without them being able to do much. Of course you need some reasonable teammates if you're going to pull this off, but it can be done. In one game I was a 27-2-2 at like 25 minutes Jinx and yet I got myself grabbed by a blitz and they killed me.