Also note such a system would have much stronger guarantees than something like Nostr (which in my view isn’t censorship resistant in any meaningful way).
If such a system was created and became popular would it mean Nostr becomes irrelevant?
Most likely not.
Lower value use cases would probably be better served by something like Nostr (or any centralized platform).
Ultimately the broadcast system could be used as a transport for a subset of Nostr events (or whatever other uses).