I've long had the feeling this is true. It started with realizing how much of public media was actually just covering twitter. Then I realized Twitter was often "ahead of the curve", but really because it created the curve. Overall I think Twitter is much more influential that is commonly perceived, though that might explain the fear that its independence brings up in the powers-that-be.
You could quibble with a lot in this tweet. If there really are around 50k "intellectually generative and curious" people on planet Earth, they're not all on Twitter. But if they want their insight to spread and be refracted against other minds, they have to go somewhere. That's been Twitter. Its moat isn't just large, it's in a different dimension than other platforms.
At the same time, Nostr is already incredibly "intellectually generative" in a way Twitter is not: its participants code, and they evolve the nature of the network as they use it and build on it. Instead of influencing the old world, we build a new one. Second, a mind can design their own experience of the network, by what they read/filter and how they publish, and so they are not subject to a central server's idea of what should be shown. This is tooling, and so consumers of platforms won't create that experience for themselves, but they're not Nostr's audience.
Watching Nostr unfurl over the last short few years, it's already becoming a home for the inquisitive and agentic who are looking for something more than web2.