The adc patch was very succesful in my opinion. The fact they aren't performing well at the moment has a lot of causes that isn't directly tied to their kit, base damage or items.
- They are the natural predator of tanks and tanks have been overnerfed and hardly see play now or just build full damage.
- Their natural predators the assasins have received several buffs for several patches now
- Supports got nerfed
- Turrets got nerfed and Baron is weak. Adc's are no longer needed to take objectives.
- Snowball is out of control: The game is already decided before the crit based adc got time to collect his items and scale into lategame
So yes, in an environment where the champs they counter don't get played and the meta is focused on early game and objective control it is obvious crit based champs won't do well. Buffing them would be terrible because it would mean to go back to square one. They would either scale faster or become better in early game and become stronger than assasins etc.
I would rather see indirect buffs that aslo improve the overall gameplay like reduce snowballing, buff towers and buff tanks so crit based adc's have a place in the game again rather than straightup buffing them and going back to square one regarding adc's.
edit: Instead of buffing tanks the amount of true damage in the game should be adressed and rageblade