I agree with you, but still think a federated and decentralised FOSS version of social media platfroms is an experiment worth trying. Those current “whole” Internet (really aspirational walled garden) social media communities are demonstrably unhealthy for society. Take out FB’s and Twitter’s core premises of their for-profit advertising/engagement business models and their rejection of open standards and you eliminate a lot of the core dysfunction of social media platforms.
That doesn’t eliminate the node moderation issues, of course. Despite its relative success in doing things like turning the Gab instance into a toxic pariah, Mastadon is still struggling with that (as Wil Wheaton’s bad experience showed). But even if (as I agree is likely) one beigist corporate instance/node with crappy, lowest-common-denominator moderation policies and a bogus commitment to “balance” becomes dominant, there will still be a lot more choices – federated with the dominant node or not – to choose from for those who want the core benefits of social media with competent moderation of your quality.