They have never buffed the freeze rate, except during the beta.
Only the slow duration and its damage.
The slow buff was to make her stronger against mobile heroes, most notable Lucio and Genji, because those are elusive. This was even given as the reason for the buff in the patch notes.
They made her freeze piercing so she would become stronger against tanks.
The fallof damage was removed to make it on par with other projectiles in the game and to make her better as a Damage dealer (this was during the fusion of the 2 classes), because she had the lowest average damage from all DPS’ers AND tanks.
But most importantly, she was buffed because she was f-tier for most of Overwatch’s history. It’s only since the end of GOATS that her pickrate and hero stats (such as avarage kills and average damage) were starting to become on par with other heroes.
Yes, she was briefly meta, but right now is she just viable.
Players want her nerfed right now because of subjective reasons such as “unfun”.
This is understandable, but at the same time may I do the same thing for heroes such as Widowmaker, Hanzo, Genji, and every other hero in the game.