whether you agree or not, asking "what's the issue" misses the point very badly, since the article is almost entirely about what the issue is (i.e. that most people will not change defaults and the default is to centralise on the bluesky servers)
At the scales these systems run at, you need large indexes. Distributing those indexes across many nodes would require a breakthrough in federated queries, and if you have one of those lying around I’d pay good money for it.