The admin was trying to get people to understand how federation works though. Most of my interactions are on other instances. That you're even discussing another instance is the admin's whole point of how your perspective is outdated. You don't need to join populated instances. You could literally setup your own and still access other people. You can actually reach more people from an unknown instance than very large ones. Many instances ban large ones due to large ones having less moderation. If you wanted to be real insidious, a corp could create its own instance and just spread posts/upvotes/etc elsewhere on other instances. As long as they don't push too hard, it would go unnoticed.
You're entirely misunderstanding the lemmy.ml admin. Sure people might flock to large instances out of instinct, but it's misguided. The admin was trying to show that user count isn't the metric you want to look at for an instance.