This is a not-to-be-understated factor, and good point.
Millennials in general, are a lot less snobby and jerk-y in general about nerdy stuff than Gen-Xers. All the classic "sneering nerd" stereotypes, whilst perhaps predating Gen-X, were certainly very present in Gen-X, and even by the time of Xennials like myself, had dropped off steeply. A lot of my earlier experiences with RPGs were of "sneering nerds" who were older than me (luckily I had a Gen-X cousin who wasn't a sneering nerd, who taught me to play). And I can say that, IRL at least, I've never been that "sneering nerd". It's outside my repertoire. I'm having trouble even thinking of a "sneering nerd" my age or younger, despite being able to think of loads a few years or more older.
And I've seen this apply to Millennials generally - and not just about RPGs - but about all games, and just nerdy subjects in general. There's just way less sneering about people not knowing stuff than with Gen-X. (One example it's easy to see this with is Star Wars - the violence with which opinions about Star Wars are held just drastically increases once you get to like 48-50 or older - 30-somethings or 20-somethings tend to have pretty soft opinions about SW, even if they are big fans, whereas it's easy to find a 50-y/o SW fan who thinks he "owns" SW and is ready to strike down upon anyone who has the "wrong" SW opinions).