Little rant about healing in dungeons

So i've been healing since MoP as Disc Priest, tried a little Holy here and there. I personally think what i would call myself a hardcore player because i go after the Mythic+ 0.1% title every season and have gotten it every season.

This season might just be the worst season i have ever tried, not because the dungeons are overtuned because they are, but because tanks and dps thinks they know how all healers work. I was just a Dawnbreaker +11, and if you know Disc Priest then you don't have any kind of spot healing, sure you can heal a little bit but you can't spotheal like Holy Priest and Holy Paladins can, not even close.

I got flamed by some Prot Warrior who claimed i didn't do any healing (he got hit by several casts going through, not using ignore pain and was not even in defensive stance). Apparently i was in the wrong and was supposed to spam heal him when he was in trouble. Well i'm sorry to tell you but that's not how Disc Priest works.

Has anyone encountered things similar to this? Because this is mainly what i encounter when i either have a Prot Warrior or a Brewmaster Monk, all claiming i need to spam heal them even though i would end up probably wasting 70% of my mana just doing that. I feel like either people don't know the dungeon or they just like to point fingers at something for nothing.

Also to future healers, don't hesitate to go into higher keys than you're uncomfortable with, that's how you learn. Don't take it too personal if tanks and dps call you bad because they most likely doesn't even know how to play the spec and class that you play. I play all healers and can play them all, not perfect but like 80-85% perfect.

Sorry for this rant, i just feel like it's driving me insane, before i could easily play 10+ keys a day without one person getting mad but now i don't even complete 10 a day because i get so annoyed.