There was once an attempt to centralize third party (user created) resources but it didn’t went well for various reasons.
Personally I like to keep resources for Krita free of charge mainly because Krita describes itself as “[…] a professional FREE and open source painting program. It is made by artists that want to see affordable art tools for everyone”. Gatekeeping parts of it behind a paywall is a bit contrary. If it costs something it should be on the merch page or for third parties they can host it somewhere else where they can charge for it.