Let me offer a bit of perspective from a player that's been playing League since early beta. Now keep in mind, I'm by no means some diamond+ player. I've only peaked at Plat 2 at best, but hopefully this helps people that main support. I've played each role plenty over the years, but during my first year or two of LoL, I focused on primarily supporting. Back in my DotA days, I mained support too. So...many...omniknight...games...and CM...and so on. First and foremost, you're going to have to accept that people will often ignore you as a support. Seeing as you aren't doing any Insec plays with Lee Sin or shadow swapping with Zed, not many will realize how much you are doing to keep your team working smoothly. Vision is a team game, but it's mostly in your hands. Often enough, your abilities make or break fights with even just one clutch heal/shield. Your K/D/A wont have much more than some deaths and assists. People will even forget WHY you died to get all those kills for your teammates. Sure, by now you already know all this, but the sad thing is, many forget what a support TRULY does. I think of it like a military medic. You save lives, you aren't necessarily meant for combat, but you sure as hell will do what you can to save people. Kind of silly to use something so heroic as a comparison to video games, but you get my drift. ;P
With all that in mind, take a step back. Consider how many people play games like LoL for glory, a sense of accomplishment, or even just bragging rights. There's such a large combination of egos mixing into one game under specific conditions required for success. Lots of people don't realize how much their team could give to make that Pentakill happen though. One Amumu ult that catches all 5 people, or a mantra'd Karma E that just barely mitigates damage that would have wiped your whole team. There's so many different possibilities. That's what makes this game so great to play for me. You'll meet some real crappy people on the internet for sure, but man...finding that group of people(or even just one or two)is a pretty awesome feeling. Don't let the bad people ruin the game for you, because you'll definitely get good games filled with good people. I guarantee that. One of those good people I met playing this game ended up being my best man in my wedding. What are the chances of that? ;D
Don't give up though. I challenge ADC mains to play support for a while to understand the struggle of the role. Laners, try jungling to get the feeling of how much presence everyone expects of you. Mid mains, try playing a tank top/jungle to know how much your frontline dies for you to get the job done.
Find what makes you enjoy what you play and play it. If you can't, take a break or find something else. My hope is that everyone that has this struggle gets past a slump like this. At the end of the day we should be enjoying this game together. We're a community and a family when it comes down to it. Let's stop tearing each other down and just play the game we all enjoy.
Best of luck to each of you guys that feel like OP here, and keep playing your favorite roles!
, 
, and am still working on 
. I have instances where I have set up the ADC for a double kill on bot with Karma only to have him tell me that I am the worst Karma ever. Excuse me? How is getting them to less than half health and backing off because I think you moving forward means you're ready to unload only to have you back off? As Lucian? And I am the worst Karma ever?