Well the issue here is that Sona as a champion doesn't work. She has the lowest bases, scalings and utility combined of the entire support class. Even every off-support outclasses her in statpoints, she's literally a hindrance to her own team and to mask this fact, players desperate to pretend she still exists build artificial numbers. Then they uses excuses and propaganda to justify their trolling, whilst denying actual facts and figures presented to them.
The evidence is self-proving, you just have to look at it impartially with open eyes. Let's take artificial numbers out of the equation, namely Spellblade and Echo. Without relying on either or both of these fake numbers as a crutch, Sona's global winrate falls below 40%, whereas her winrate in Diamond+ falls to an even lower less-than 35% winrate.
She's disappeared from competitive play completely, she has the lowest pickrate of any champ played into the support role professionally. That not only means Taric is being picked over Sona, but also off-supports like Syndra and Kayle are more likely to be played support than Sona.
...and when did all of this happen? After patch 4.13 went Live, that's the exact moment in time that can be pinpointed as when Sona disappeared from this game. Yet in spite of all of this, not only does Rito deny the fact that she's the weakest support and amongst the 5 weakest characters in the game overall, they continued to nerf her further and still threaten more nerfs to come, every time the issue of Sona's nonexistence in this game becomes too publicly widespread. In fact, every appearance she has in the patch notes since this game's creation has been an overall nerf, she's never received a true buff in League's entire history. It's pretty clear to anyone with an objective view can tell that Rito as a company despises Sona and don't want her to exist in this game. I've 1st-hand accounts from up to 8+ different Rito employees in 4 or more separate work teams publicly stating their hatred of Sona and I could name them all off-hand if need-be.