Q is missable, unless you are almost in auto range it may just hit minions instead of the champion, at which point you are wasting mana and shoving the lane. Since the rework over half the actual power of the ability is tied into the follow-up auto attack which simply gets you KILLED versus competent players on the other side. (Seriously, if you are brain-dead enough to attempt always getting full power from your Q you are a bad Sona player that is asking to be jumped on and deleted.) Also the damage is laughably bad, Sona absolutely requires items with artificial scaling to be remotely useful past lane phase for any damage.
W is overpriced for what it does for all of lane phase. They balanced it around a full five man usage pattern come team fights... which means for that first 10-15 minutes of the game its almost worthless. And it only gets remotely usable with a full-AP build, which on a support is build-path locking.
E is the biggest joke in the game since the rework. Sona has no wave clear, she used to be kinda able to work around that by speeding minion waves up to soft counter-push. Also it had an always-on portion that helped rotations. Its a one point wonder for practically the entire game now.
Power Chord is enormously nerfed. Sona no longer has ~7 second cooldowns across all abilities, power costs for a quick reset are exorbitant, and it requires her to be in auto-attack range to use... which on a squishy champion with some of the lowest health and resistances in the game that has to be build full-glass to be remotely effective... is asking to be jumped on and killed due to also being in the lowest speed category in the game.
Ult has a stupidly long cooldown and is literally the only thing a Sona that is behind can contribute, oh and she may as well be gated by Flash cooldown because she is so squishy that attempting to use it for anything but a counter-engage without flash is suicidal. And if you end up spending that ult saving your slow Sona while warding you may as well consider the next team fight as lost as if they already killed you anyways.
In some ways playing Sona requires a greater degree of positioning knowledge and map awareness than any other support in the game. And she is practically the face of the support version snowball or fail since the rework. She has no effective fall-back pattern. If behind she will stay behind unless the opponent royally screws up because again at that point she is literally nothing but an R dispenser once every couple minutes.
