"Guys" (without a "the" in front of it) is uncontroversially gender-neutral in most contexts in at least some parts of the US. I'm not sure whether folks worried about it are from places where it's definitely not, or places where it's not used much at all so they're not aware that it's a non-issue in (at least many) places where it is.

I do prefer "y'all", though. I think it's the best one we've got, of the options ("yous" being another big one, and ew, gross)

I also love the nuance of "y'all" and "all y'all".

The joke is that the person "saying" this is wearing their "I'm a rational, independent thinker!" tech uniform (expensive Nordic outdoors wear, so practical, so smart, so active, Vimes' boot theory, et c, not like those clowns in business wear, I'm interested in practicality not signaling, that's why I'm spending so much money signaling so hard about how rational I am).

They are visibly displaying a complete lack of personal taste, instead wearing the SV equivalent of an outdated-cut, off-the-rack navy blue (or even black, LOL) business suit.

The joke is that the message "good taste is what matters now" is being delivered by someone apparently, in a specifically SV sort of way, with a deficit of good taste.