i think its a combination of things thb. on the one hand efficiency and speed running,then lack of communication, then min-maxing mentality which is very wide spread then it was maybe 10years ago, general impatience,assumptions that everyone knows the job they are playing as or the encounter they are in and ofc not to forget the expectations. this is all in the context of duty roulette's but does to a degree also apply to party finder groups, thou in party finder you can set your rules and everybody knows what they sign up for.
i don't think "WoW" or any other game from a similar genre or online game in general has a fault at any of that, the gaming community and mentality is pretty much the same everywhere,slightly worse or better in some cases.
one could make a case for as to more solo friendly a game becomes,the more the social/socializing aspect becomes a "nuisance" and its easier to be impatient with others or point fingers at them. the more you play with people you don't know and probably never will meet again, the less you care about them and being an ass to them or what they think about you(your reputation).
i think in this regard the upcoming "wow classic" servers and the gaming community and industry reaction to them are very interesting to me, since its a game from a different era of games, no queues for dungeons, you play with the people from your server only and your reputation matters something, tanks are meant to take the dmg and not deliver as much pain as a dps job would, dps get 1-2 shot if they pull or get aggro, crowd control matters and healers are there to heal, not to dps. resources have a significance and so on.
also i agree that people are very thin-skinned nowadays,not only the gaming community but overall.
ps: i could write and talk more about this topic, but no one likes reading a wall of text or an essay.