First of all there no such thing as KS, its a team game. Of course you want your carries fed an as a support, kills aren't really doing you much good because your not building damage items. If you allies are standing around with low health there isn't much a lulu bubble can do to keep someone from dying, its meant for damage mitigation not invincibility. Unfortunately as support its our job to protect an set up plays for carries to take control of the game, when this doesn't happen the blame is easily pointed toward us. When its the other way around when a support is doing all those things an the carries get fed all the glory goes to the carries its just the nature of the beast. If you did the best you can do then your not a bad support. A lot of this game is about decision making an following through with the decision that was made.
Example, I'm supporting an ADC during lane phase. I have bot lane completely warded an there no way a surprise gank will occur. Enemy jungler comes in, I move to a safe distance, ping my ADC warning as the jungler continues to come to my lane an destroys my ADC. I did my part, a 2v3, my ADC is at half health, has plenty of time to reposition, gets advanced warning, yet chooses to continue to CS. There nothing more I could have done but to feed the jungler or ADC more kills. It was his/her own fault they died, bottom line not if there weren't any wards, pings, etc then the fault would have felt on me.
This game is a digital version of chess, as the game changes, us as players has to adapt. So as long as you did all you can then you shouldn't be doubting yourself. In addition you can always exercise your mute button when people are flaming you.
Hope this helps - good luck on the rift.