She’s objectively balanced right now. Even if her pickrate is one of the higher one’s her statistics show absolutely nothing that points towards her being overtuned. She’s the only dedicated healer having mechanically no equivalents as main healers and she has very high team synergy with the current meta roster (unlike other main healers) so her pickrate is naturally bloated.
When you consider all these factors there’s just absolutely no objective reason to nerf her currently and the only valid subjective reasons to make changes to a hero are that an ability is unfair (hog’s hookcombo, scatter arrow, Doomfist, Sombra) or fundamentally flawed (Mercy’s hide n seek games, Sombra’s hack changes) and these are things that the developers work out only internally
If you want to fix problems with the supports then you should be looking at Moira’s resource management problems, Ana’s lack of healing numbers and Lucio’s ultimate being rather irrelevant under current meta.
You can look at average statistics of support heroes across the ladder from here: