Nah "there's no girls on the internet" jokes in 2023 (or current year) are kind of cringe, and the only people I hear say jokes like that (even ironically) are in their 40s. Lemmy skews older, so I can see why we'd find that funny.
If we're going to be pedantic, it's "at LAN parties".
And our experiences are very different. I went to a lot of LANs in the 2000s with my parents where there were many women participants. Not quite 50/50, but a sizeable percentage. 0% women at a LAN sounds like a culture issue to me.