It does sounds kinda like a qq post, but the points you made were valid. I play support alot, but never really payed attention to the variety of nerfs to accross the board support 'jobs'.
Now, I know in reality, each 'nerf' only affects one or two champs at a time for that job. Like your example about Janna's nerfs to her utility doesn't reflect on Taric's or Leona's ability to stun people. Or Nunu's ally buff's and enemy gimps. But you are right that every role has hit some heavy nerfs that have piled up as time has gone on.
I hope that at the very least we can get some Sona work soon, which I know some reds have mentioned happening in other threads.