You just need more practice and experience with ADC. I really understand. I felt the same way when i started out ADCing i hated it it, but i grinded through all the practice and games and i can say im at least a decent one now, and love taking the role with alacrity.
To answer your question though if youre really behind on farm and levels then the priority should be you catching up and hoping your teammates can and will turtle and defend as best they can on their own, to create space for you to freeze the wave and farm a few waves, and hit your power spikes. If your team is failing to defend and turtle under the turret properly, and the enemy is getting damage on your T2, that would be the call for you to assist no matter how far behind you are. Defend the turret and go right back to farming and pushing when its safe, and rotating lanes after every few waves if needed.
If however you have a team that is just hellbent on death matching with every bad engage they take, you're damned no matter what you do. If your team can't turtle, cant initiate properly, cant maintain vision and objective control, then there's nothing that you as an individual can do no matter what situation you're in. There have been countless games where I've completely outfarmed everyone in the game, but we still lose, because the team as a unit is not working together, let alone working with the ADC they demand be good.
This is in my own words of course.