That is incorrect.
Sona not building AP makes her useless. Literally, she becomes the worst supp you could have if you do not build AP on her.
The real scapegoat is claiming the Sona has any real form of Sustain or has unfair poke.
Her w heal is garbage, and she WILL run oom after 2 casts. Maybe 3 if you have good utility masteries.
All of her damage value's are lower than Nami in a full rotation. Nami does more damage unless Sona buys a sheen. Nami heals more unless Sona builds AP. Nami is and has a better speed boost unless Sona builds AP.
If you are not building AP on Sona, you should not be playing Sona.
I would also like to ask that you stop acting like you know what you are talking about. You are very much talking out of your ass.
Just because you get wiped by Sona in lane due to you not knowing how to fight her is your own shortcomings, not the champion being OP.
Also, before you try to mention from your experience, you are in silver. I am as well. I have watched various Sona mains and players in high elo. In fact, the current best Sona player in NA, himself has said that Sona is very much a lesser champion than Nami. Her only benfit is that she is more constistant in her damage, but Nami has 100% more potential.
Literally any supp in this game besides Janna can easily set Sona up to be nuked from the botlane. Sona is not popular in high elo for a reason. Sona is only useful as a poke supp who scales into a secondary ap carry. Her heal is only good mid-late game with AP, as well as her speedboost.
And before you say that is Toxic, Annie, Zyra, Vel'Koz, and Fiddlesticks are used as supp's for the same reason.
Sona has less damage and cc than them, and also less mobility.
Her heal seems to be people's reason for saying she is op, when it is not reliable in any way in lane. Using your heal to constantly heal your adc will cause you to go oom and be useless. 3 w's will restore only 200 hp at the most at rank 1 (If your adc is at 1% hp for each heal). That is 240 mana for a 200 hp (Going to be way lower in normal circumstances) heal. That is garbage.
The only reason to play Sona is to have a secondary AP carry who can provide utility in the form of buffs to her allies. She cannot go mid due to awful sustain and even worse waveclear.
So before you go spouting off nonsense about how "Good Sona's built utility. Sona does not need AP", you should do some research. Know what you are talking about before making yourself look like an uneducated "Bronzie".