Did you witness a cultural gap between the culture of the younger cadre of designers an writers then their gen xer counterpart? (Does gen x nerd culture can co-exist with it's tumblr counterpart?) In your experience does fandom play dominate role in your line of work?
i admit, i'm not really sure i parse what kind of answer you're looking for here, but it's been a while since i got a work-related message, so i'll do my best
is there a cultural gap between younger (i assume you mean game) designers and gen X designers? yeah, probably, but how much of that is normal generational divide? how much of a cultural difference is there from year to year in gamedev, or from project to project, or studio to studio? people who've done mobile or solo indie projects for their whole career will come to a project with different expectations from people who've only done AAA.
i've met older devs who pine for The Good Old Days. i've met others who said, "yeah, we used to sleep under our desks, thank god we don't crunch like that anymore." everyone's different.
can gen X nerd culture and tumblr nerd culture coexist? sure, if you want them to. i was born too late to experience gen X nerd culture firsthand, but i've never felt bashful about admitting i had a long background in tumblr fandom. i tell coworkers who aren't familiar with it that it was an interesting milieu to grow up in, and i've learned a lot, both good and bad, and all of it has been useful to my writing somehow.
i've never had an experience where an older coworker thought i was weird for making a particular pop culture reference or anything. in fact, i've had times where i was able to put some authority behind an argument with "i've been around shippers for nearly twenty years, i know what they pay money for." the trick, i've found, is to have a sense of humor about it. (not that tumblr invented shipping, obviously, but you get the idea.)
does fandom play dominate role (?) in your line of work? depending on what you're asking, this could go a few different ways:
is RPG game design primarily influenced by what devs believe will most lead to an active fandom culture? not that i've seen, no. fans and devs have a complicated relationship. the "fans are entitled" vs. "devs are jerks" discourse can be a real tar pit. devs do make design choices based on what they think will make a game most engaging, and with sequels, that can involve "what treats do we give returning fans." but it's sort of up to an individual artist or writer to go "i'm making XYZ choice because i think it will be fanfic bait."
do you, as a game writer, make most of your creative decisions based on the kind of fanwork you've enjoyed doing in the past? i imagine on some level i do, but that's just me. i enjoy exploring the same themes in both fan stuff and original work.
do many game writers have a fanfic background? more than there used to be, or at least there are more now who will openly admit to it. again, the "fanfic writer made good" class of author gets... you know... there's discourse, but all the fanfic-brained colleagues i know are amazingly talented. they have great instincts about how writing decisions will land with players emotionally, and they don't feel limited to the same one or two "classic" plot models.
hope some of that was useful!