I don’t mean universal in the sense of “totalitarian”, I mean it in the sense of “large common denominator”.

Do you think that the conversation around, e.g, python programming or wood turning techniques will vary so much that it warrants many specific flavors?

it’s likely to be skewed towards whatever culture exists in western english-speaking countries

This is good enough for most people and does not hinder the ability of those that are in the minority to create a different/specialized community.

Centralization/decentralization is a spectrum. No one is proposing to force everyone into a single box. The idea is only to combine efforts for the things that exist in common and to avoid unnecessary redundancies.