Janna is an interesting champion. Though she's not in a seriously unbalanced state, some vgu might be nice for her after the main-concern champions get reworked. For one, her forecast's zephyr needs to have it's animation last longer, and her hair def needs the new visual mechanism discovered for sol's tail and yorick's cape (right now it looks as if it's just a giant stick with too much hair gel, and she swings it around when she turns like a baton)
Thematically she is really lacking in that wind/weather feeling. For example azir players actually gets that emperor feeling, when you verse sol you'll certainly be gazing at his stars, taliyah's overall mobility makes her feel like a little pecking bird trying to go from branch to branch while her cc like weaver's wall and the stone traps gives her that sense of safety from mother earth (the great weaver); jhin's abilities literally test your sniping skills while that spine chillingly calmness between autos make you feel like a cold blooded killer; if you think about it, all of these cleverly designed kits and many more really helps you appreciate the theme of the champion. Janna has none of that.
A good question to ask is, if you remove all of her particles, and the names and any other artistic references to "wind" or weather, would you still see her as a windweaver? Same with lulu, if you were to remove all of her glittery particles, would you see her as a fae sorceress? Not really. You can literally swap the two themes and particles, and they can still fit quite well. It's true that Janna is balanced, she has her footing in a player's selection of supports. But "super fun and exciting to play"? "unique in play style?" "aligns with wind/ storm fantasies"? No, i don't think so.
Right now, you can either wait for riot's roster update, when they are going to update supports (enchanters) and hope they include janna in it. Or wait till they finish updating all the champions that people listed here and in other places that's more significantly unbalanced than janna. If you ask me I wouldn't rush for just a visual update, purely because a full vgu might be more exciting.