Do you have any evidence that "John" isn't being lazy? No, you don't. You keep striving to make a point by trying to come to the defense of people who play poorly by using nothing but hypotheticals, you can't accuse people of having no evidence when you are doing the exact same thing, basing every single case of someone playing poorly by pulling the "You don't know their situation" card. You can't have your cake and eat it too.
Like Hyomin already mentioned, If you have a level 70 tank and have no idea how to hold hate, use cooldowns properly and know the mechanics of the bosses you do not get a "get out of jail free" card for poor performance and inconveniencing your group just because you happen to be the level of the content you are doing. Your entire argument is that every single person in every single dungeon that you end up with gets a free pass regardless of how poorly they play just because we don't know that players life story and should therefor make the entire group suffer poor and lazy performance based on nothing but hypotheticals.
I'm all for giving players the benefit of the doubt, especially when i know they are new, but no one in their sane mind is going to sit there, dungeon after dungeon suffering in silence while the entire run falls apart all due to your argument of "You shouldn't judge or assume why this player is playing this way because you don't know them or their circumstances"
I cannot even begin to fathom how much worse runs would be if we never removed poor players that are proving to be detrimental to group progress all because of "You don't know their story" and just let everything spiral into chaos because you don't want to offend them by assuming anything about them or their playstyle. Please just stop, this entire thing is ridiculous.