It’s certainly a great read and is worthwhile, however I fundamentally disagree with the base premise that the goal of a federated system is to be uniformly distributed.
Why should an instance focused on a niche topic have the same representation as a general instance? Why should either have the same representation as one with abhorrent content?
Choosing your instance is effectively a statement that you agree with the mission of the particular instance. The number of low user instances demonstrates that there are a great number of people that share the author’s vision of federation.