Sona never gets to have her end game fantasy.
Disclaimer: I'm not asking for sona buffs. She has a high win rate as is and I have fun playing her.
The bonus CDR passive is strong and fun to use, however it's gated by levels. The 40% reduction requires level 16, which almost never happens in ranked games for supports. Supports get less exp by default due to the necessity to leave lane to ward and back more often to recharge wards. All exp gained by supports is shared exp. If I unlock the second tier of Sona's ult, it's already a long game. If I'm at level 16, I'm probably playing a normal with people who don't push objectives.
This differs from other supports since the full effect of their ultimates are usually felt at level 6. Extra levels usually just mean more damage. More slow. More healing. Leveling up those ultimates don't have the same 'feel' as leveling up Sona's since it brings so much to her entire kit.
I get that the full effect of the level 16 spammy spells is powerful, but it feels bad to know it's there but never get to use it in ranked.