Throwing lanes and games as Sona.

I've recently gotten back into this game and have decided to main as Support, and I've always enjoyed Sona's playstyle. However, this return on a new account has been a rocky road and as Sona I am finding myself to be a liability to the team until I get that dream Ultimate - with fingers crossed that I haven't caused my team to lose by that point.

Here are my issues:

I lose pretty much every lane, especially to kill lanes and Blitz/Thresh lanes. My poke is considerable but if they can retaliate in any way shape or form, that's it for me. I can't escape anything due to my low MS, and I can't properly respond to or juke Blitz/Thresh hooks in the absence of a minion wave. I die in four auto-attacks.

Having played this game way back in the beginning, I understand that Sona's infinite sustain and crazy poke is toxic to play against, and therefore it is necessary for hard-engages to punish her. However, I am at a loss trying to understand why she still has health parity with a minion. I'm not sustaining jack all anymore compared to what she used to be capable of. I'm not doing the damage that I used to do. I don't have the CC or utility of Champions like Thresh. I feel like I'm building items to just reach PARITY with the base capabilities of other Supports, nevermind building items to exceed base effectiveness.

So why may I ask is it so abso-freaking-lutely necessary that the enemy be rewarded with a kill on me in every engagement? Is my ability to heal 30HP for 1/5 of my mana bar too critically oppressive to the enemy team that I have to die immediately to the next light breeze?

I really enjoy this Champion but I swear, I feel like I'm just getting farmed for wins at this point. Thresh players emote, laugh, and taunt the entire laning phase. They know as well as I do that the second I make a mistake I'm dead, and the moment I make a second mistake, it's a tower. They know it and I know it. They also know that they are free to make a myriad of mistakes that I cannot punish. It's also frustrating because I'm trying to get back into the game and learn how to Support properly and I just have this sneaking suspicion that some of these kill lane Supports are not actually Support players (they buy the warding item and then build damage.) They're top laners and Junglers and whatnot who didn't get their role this game and are rolling a kill lane hoping that that they can get the snowball going to cover up the possibility that they cannot nor do they have any interest in playing Support because it's "boring."

And it's just embarrassment after embarrassment. If the enemy Thresh isn't laughing at me then my team is taking notice of my feeding or lack of impact. I'm not factored into the enemy engages (because I don't need to be factored into it most of the time), and my team doesn't wait for me for fights. If my lane is actually going decently well then the fed enemy Jungler waltzes on down and 100-0's me in less than a second. If my team is behind at all, then 3-4 Champions on the enemy team are capable of killing me in less than 2 seconds. Half the time I'm dead before my ult registers as going off. I hear the audio que and sometimes visual, but I get killed before the game registers activation.

I'm just confused. Maybe I'm bad. Probably I'm bad. But seriously, WHERE is the payoff, the upside, the silver lining, whatever, of Sona having no defense, no movement speed, no health, and no mana? I can't do anything. It's 4v5 in 75% of my games.