This is a categorically false premise. The kind of statement that only makes sense when you're in a deep bubble and entirely removed from the average person's use of the internet.
Deliberately removing yourself from Google is fine for the author who is more concerned about taking an ideological stance than they are about being discoverable, but removing yourself from Google is terribly bad advice for anyone who wants to help people find their content.
Many people do use Google to find content and people, even if you don't.
I mean no harm by this comment, but I think you're the one living in a bubble. Do you watch high school students using the internet? Where do they go for information? Reddit is the first place they look. Then they look for a Discord server. Google is a last resort, but since they know it's probably just going to return crappy SEO spam articles, they may give up entirely without even trying Google.
Your answer is technically accurate, but only in the sense that it disproves the "nobody" part of the statement because of the population of users age 45+. Google has lost their place as the site to use when you want to find information.
How? Are there ways to search for discord servers that might have content you want inside of them? Like, directories of discord servers? I'm genuinely curious because that would be very useful.