I think the fear that Nostr is too centralized right now is a bit overblown. With such a small group of users, all with similar ethos, there is no pressing need for decentralization right now because there are so few risks even if things are centralized. When the user base grows into something more substantial and starts fracturing into different ideologies and interests then decentralization becomes a lot more important. IMO it'd be a waste of time and resources to build out large swaths of infrastructure and services just for decentralization's sake when the demand for those resources just aren't there.