I don't think it's possible to get an S on Janna anymore.
League of Legends Match History
Went 0/0/17; Adc also never died. Most (25) wards (3 pinks).
Participation: 63% kills, 75% towers, 100% drag & baron.
I could understand an S-. There was a teamfight I was late to (although still in time to impact it) and I tried roaming top to save gnar from fizz, but didn't get there in time (twice). But honestly, aside from that, I have no clue what I could have done to improve.