... is supremely unconstructive, pointless, and only exacerbates the issue. Telling someone that they're bad when you're so impatient as to ridicule them after they fail to the same mechanic three times; telling someone they're bad when they declined your unwarranted, unasked for, and unprompted "feedback"; telling someone they're bad when they just want a stress-free, casual experience of this game - these are all behaviors that are rotten to the core. They reek of elitism and ableism, and belie a hollow core of morality, in which any shred of empathy can not be found.
It is therefore beyond disappointing to see community leaders and content creators chide those who are slower at improving as being 'bad'.
First of all, not everyone is able to learn at the same speed as you. While it might take you only two or three tries to comprehend a mechanic, someone might take fifty times - and that's OK. This game is not a job and there is no metric for players to meet. We are here to play the game, not to fulfill some arbitrary performance metric like in an Amazon warehouse.
Second of all, people can and do forget mechanics over time that they have not seen frequently. Not everyone no-lifes this game for 10 hours a day to instantly recognize every mechanic that they see. Do not assume that people are locked in the basement as you are to be able to perfectly memorize every single mechanic and rotation in the game.
Third of all, it is the height of ableism to assume that everyone playing this game can dodge AoEs perfectly all the time. People do and will age, and reaction times do grow slower. Complaining and insulting a player as "bad" because they stood in an AoE can and often are instances of ableism and ageism, by indirectly insulting their decreased reaction speed as they grow older.
What makes a "bad player" is not failure at improving. What makes a "bad player" are those that go around personally harassing, insulting, and picking fights with other players because of some self-conceived notion of good and bad. Get off your high horse and let players enjoy the game the way they want to.