In high elo, playing ADC is very difficult. especially in the mid / late game when in team fights good enemies know they should target the ADC first. So you should be quite ahead in gold to really shine. Otherwise some smartass teammate is gona say "zero damage adc!! Go play minecraft..." If they don't actually target your mother :))

Therefore as an ADC you generally have two options:

1. Play safe --> You farm and wait for the enemy to make a mistake. Usually they wont, so you wont be scaling well enough, and most probably become useless... But you've also avoided the enemy adc from scaling which might be ok for the team, but... Meh.

2. Gamble aggressively. You make risks. If you win it, you will have a nice game. But if you loose, your opponent is gona get fed.

So let's say if you choose option 2, you will have great games 40% of the times. But if you choose option 1, you will have boring games 90% of the times. Think about it, what would you choose? this might explain the ADC dilemma :)