Is there anything that would be a viable alternative?

I try my best as support and I consider myself pretty good at it. I CV where I'm told/believe their team to be, ward everywhere (Baron, dragon, ours/their buffs, bushes, get oracles and clear wards, buy aegis/shurelyas/randuins and use them...but always someone either leaves or the carry is just terrible or someone just feeds...

I'm usually support because I care about team comp and I know everyone else hates it and probably won't do it, and also because every support I see is just god awful at it...

Should I pick supports like Janna and Soraka and just start as support and try to go AP?

Also, If someone disconnects, should I just drop support and go pure AP? Take whatever lane they left and try?

Or should I try someone more tanky like Alistar or Nautilus? Or maybe even Blitzcrank?

Is there some kill lane that won't get me raged at that could work well enough so I can carry if I have to? Someone like Mundo comes to mind, since he needs little farm to dish out damage on people.

I played support morgana once and went AP out of that to carry a game. Dumbass tryndamere couldn't carry. Nobody expects a hard carry from support position. I think nautilus and blitz depend on their team too much to carry a game unless they're amazing (I've carried as jungle naut a few times, but not support)

Basically Soraka, Janna, Sona, Taric, and Lulu can all play passive bot lanes perfectly fine. By passive I mean 0 cs supports with scores of 0/0/0 at the end of the laning phase, and they won't come out too behind, since their primary contribution in team fights is utility from a distance. Zilean also can too but by his nature he tends to poke a lot and force stuff to happen bot.

On the other hand, bots like Alister, Karma, Nidalee, Leona, and Blitz are all supports that can perform amiably in a passive lane but truly excel if they can get some gold off of kills, assists, and even minions if their carry recalls after a skirmish or kill.

The problem with kill lanes is that they aren't viable against good players who counterpick it with a safe ad ranged carry like cait soraka; cait can farm underneath her tower and soraka gives her the mana to do so (there are other combos, that is just one of them). That doesn't stop you from using them against weaker players though, as gaining the skills you need to use them and defend against them are what will make you a better player. After all, if you're 1800 elo but can't handle a kill lane since nobodies ever used it on you, that's a pretty big weakness, and being unable to exploit a poor lane comp with a kill lane because you've never tried it is also a bad thing.

Another problem with kill lanes is that ad ranged carries tend to be weak early and so they're not that strong of a kill lane partner; this means they're both vulnerable in other lanes and poor as kill lane partners (obviously with exceptions; Tristana is a good example). In order to really execute a proper kill lane you either need to win the game early and shut down their ad so hard they can't recover late game, or you need to communicate with your team to have a backup plan in case that fails.

From my experience as a support player, the way it breaks down is generally this; the tankier you have to build, the more aggressive you have to be on lane. Leona/Ali/Blitz being the big ones. Luckily, most of the tankier supports are also the best choices for this. If you go the more passive rout with auras/your NOT the main initiator for your team, you usually don't need as much gold. Soraka being the prime example, typically.

Obviously this isn't perfect, but it is a decent generalization.