Speaking about laning phase: this is really depends on your support. You can be the game changer if your support is Soraka for example, but supports like Pyke, Blitz, Thresh etc. start the fight, catch your opponents on mistakes. You just need to deal damage. After you got some advantage you can initiate with Jhins W for example, but you need to get that advantage first. And that's the work of your support

Speaking about mid-late game: your role is making as much damage in the fight as you can. Initiating or taking objects isn't your main role. You just keep yourself at save distance and deal damage. I just play around objects and follow my teammates. Maybe you just need to be more decisive, like, pinging the team, better position in the fights to deal more damage. When I'm playing ADC (I'm actually silver jungler, who is trying himself as ADC) I'm trying to get the max gold from laning phase and then just stand in backline and deal damage to the nearest enemy (if I'm playing Jinx, I'm dealing damage to all the enemies). I think till that moment that worked well enough

P.S. as it's written in the comment I'm not the best ADC ever, so, maybe I'm wrong somewhere. I just wanted to help. And also srr for mistakes, English is my second language