Why is everyone saying no damage? She doesn't NEED to do damage she is one of the most impactful champs in the game. She has no sustain, yes, but her shield makes it VERY easy it win trades early. Her shield can block one auto early on and gives bonus ad. That's huge early. She's not going to dominate a lane, but it's rare you see someone dominate a Janna lane. She can babysit ANY late game adc and basically guarantee them they get late game. She can kite anyone in the game and makes champs like Shy, Trundle, Skarner, Volibear useless.
She has immense speed, cc, slows. I'm not saying she's unbeatable, but she's far too strong and has no real "meaningful" weaknesses.
What you guys are saying isn't meaningful. No damage? She doesn't need damage. Weak engage? She doesn't need to engage. She's squishy but 60% of the supports are and the way she works you're not going to simply kill a Janna.
And she's not even hard! Like you don't have to be a master at Janna to win games. You can tell a good Janna from a bad one, but you don't really need to do much for the amount of impact you have on a game.