I was gonna make a thread on Sona's half-assed state, but I wanted to wait a good while before doing so. Still, you and me tend to be on a similar page, so I'll share my thoughts with you:
Sona's whole kit needs to be revamped big time. Her kit's literally confused. Everything of decent value in her kit requires her to get extremely close to opponents + she has no mobility, no hard cc in her basic kit, and she's incredibly squishy. One could say "So increase her values to make fighting this close to enemies worth it", but she's so mechanically simple Riot can't increase her values. On top of that her simple-yet-effective ult makes it so Riot can't really do much with her basic kit anyway since it's a relatively wide, straight, stunning line, making it an extremely valuable ult on a pretty piss-poor kit. And this means Riot can't buff Sona because she'd low-elo stomp way too hard.
Either Repetoir or Meddler are already on the record saying that Sona's rework was done on a low budget, hence why it didn't do much for the character in the long run. If they were to give a rework to her any year soon, even if they kept a move or the passive the same, her play pattern needs to be altered. Either make it so she plays more like a back-line support or give her more benefit for having to hover in everyone's faces 24/7. Regardless of which she's given, she needs better cc options (hard or soft, but for the love of goodness something), and her W needs to be looked at because it's needlessly over-complicated to the point where most people don't realize that half of it is a shield and the heal only heals like 30-40 health until I start ranking it. Sona's just lacking basic shit that you'd expect her to have as a support, and that stunts her ability to be used efficiently beyond like...Gold elo. And yes, she IS countered by almost everyone in the support cast. Any support that's actually good as a support right now has advantage against Sona so long as they know how to play the match-up. Nami can bubble Sona since she has to get in-range to AA her target, and then have her killed. Janna's shield eats Sona's Q and then her adc can trade for free. Soraka can heal her adc and fish with Q's from way out of Sona's range. Anyone with a hook sends her running. Alistar's her worst match-up in this whole game, and to boot he can freaking heal himself...like that's one of the main things mage supports are supposed to have over tank supports and Ali's like "nope!". Only supports Sona can be are like...Annie, Zyra, Lulu, Brand, Kench...people that kind of need updates/buffs of their own or don't belong in bot lane. This is all due to the fact that she's got the stats of a back-liner, but the play pattern of someone that has to be way too close for comfort...and her gains for being this close all the time isn't even worth it!
If they ever do announce a rework of Sona, the last thing I wanna hear is "We aren't gonna make too many changes/We're gonna keep her relatively close to home". No. MAKE BIG CHANGES. The problem with this champ is literally the entirety of this kit. It's heavily related to something Riot doesn't believe is healthy for the game anymore (auras), so this aura-based kit has to go. Do something else sound-related that isn't auras that you guys wouldn't mind supporting in this game. Stop with this half-assed attempt at making Sona something you don't even want in the game, Riot. I'm tired of feeling like my champ is nothing but a nuisance now that I'm not low elo.