The biggest problem I see is people don't get the support role. You are the bot lane CARRY for the first 10-20 minutes of the game. Most ADCs don't have the damage to actually kill someone that early into the game, that's why they rely on the support or the jungler to help. Your job as the support is the help them get to that powerspike so that they are ACTUALLY USEFUL.
Vayne has a horrible laning phase. Yeah, only if the support she's with does nothing to help her. Had a game as Lulu with Vayne vs a Ziggs ADC Brand support lane. AOE damage is Vayne's worst nightmare, so this should've been easy for them to win. So, I stood up in lane, away from minions, and tried to be as annoying as possible. They were using everything to try and hit me, which meant they couldn't use it to push the wave. We actually kept the wave in the middle of the lane or pushed to their tower for most of lane phase until their jungler came down. All I had to do was stand up and dodge the skills shots aimed at me while occasionally trying to hit them.
What people need to do, in my opinion, is play a champion they know. Ahri is obviously not a support. But if you are an Ahri main, you already know how to play her, which means less you need to learn. Obviously a tradition support might be better in certain match ups, but if you actually know how to play your champion, you are probably better off. Plus if you are playing something like Riven support, it's not like you getting kills is going to hurt the team.