Unpopular opinion : Winrate is NOT an OPness indicator.
On this website we can compare winrate and playrate by patch.
Remember,
was nerfed last patch : her shield decays over time, and enchanter items got nerfed.
's winrate progression : -0.3%
I mean, for such a big nerf to her, she only lost 0.3% winrate which is NOTHING. If winrate were really representative we should see a much higher number. + the meta doesn't particularly favour Janna, as she doesn't have as much adcs to peel (with whom she excels the most)
Secondly, see
who is at ~44% winrate that still is played by proplayer_ because he is strong enough for being played_. (source : https://www.probuilds.net/champions/details/Ryze)
winrate should NOT be an OPness indicator whatsoever, because it simply doesn't mean anything. Using winrate stats should never be a thing.
has a high-winrate because he's really difficult to play and most people give up on him after a few games, leaving one-trick who learned the champ and are really good at him. Doesn't mean he's broken