I see Nostr as an experiment in what happen when you empower users with their own cryptography.
Right now NIPs function as a free market of ideas, over time the most effective ones will become increasingly interoperable, and less popular will remains niche.
I'd say everything will never be completely interoperable, as some client will push for more decentralisation, other for speed, etc. You as a Nostrich will have the freedom to choose how you want to explore the Nostrverse