People say that, but the sales didn't really change anything. The site still looks pretty much the way it did back in the day.
I think the main thing is just that Slashdot "belonged" to the BOFH / sysadmin subculture that's largely gone. In my younger years, that was the tech career to aspire to. Nowadays, kids want to work at OpenAI / Google / a billion-dollar future unicorn, so the SF Bay Area ethos is dominant.
/. withered away because it was sold off multiple times and lost its mojo.