Only thing that makes M+ toxic is the players that don't know what they are doing.
When running high keys there is little or no chance at failure. Miss a interrupt and it could lead to a wipe depending how the party's health is. Example: Golems in SoA, those bad dudes can kill you.
It's not toxic to expect someone that joins high content to know what spells need to be interrupted, when to use personals.
As a healer I track people's CDs, I'll always heal a person that has there personals on CD over someone who doesn't. Oh you died because you were staying in "fire" but your CD isn't on CD, sorry the other dps who's cd just ran out needs me more.
I don't understand how people are called toxic because they are pushing higher content and expect other people to have a clue what they are doing. Do you plan on raiding without knowing the tactics, it's the same thing.