You can blame this all you want on evil social media corporations, but the reality is AI companies scraping public conversations to feed LLMs are the current reason for walls being erected around every single garden. Facebook, Instagram, Twitter, Reddit, LinkedIn.. all heading toward full walled garden mode to prevent scrapers from repurposing data and profiting off their systems.
Federated systems are a nice idea, but they're not funded and will crumble under the same pressure until they too go into private mode. It's simply not a financially sound decision to run an open node that is continually harvested by corporations seeking to profit off the conversations occurring on your platforms.