Nobody outside tech cares about decentralization or federation.
At some point, everything converges to centralization.
No amount of Mastodon servers or any fediverse self hosted instances spun up will change that.
There is a reason that mastodon.social is the biggest instance and that they couldn't close registrations to promote decentralization.
Hell, I would even say that threads is the biggest mastodon instance.
In the real world, you can ask people if they would prefer to live in a town with all bespoke mom'n'pop businesses or just a few big box retailers and chain restaurants identical to the ones in the next town over. The intuitive expectation might be that most people would prefer the bespoke stuff because it offers a more personalized service, but it turns out that many people really do want to have the same experience as folks in the next town over. Even among folks who claim to be free thinkers or unique personalities, even among folks who have xenophobia or express a chavinistic sentiment, there is still an impulse to seek the exact same experiences that folks outside of their community are also having. Why is that?
I am sure there are various psychological and perhaps even physiological reasons why people are drawn to homogeneity, but the bigger problem is that bad actors can find ways to exploit these reasons to amass power. Once those actors have the power to shape society, then it becomes a feedback loop where perhaps in the abstract a person might not desire exactly those experiences that are provided by the central authority, but because the structures in society are now pointing toward that being the "best" option, then that's what people come to believe they want.
I suppose the philosophical question is if people come to want to be exploited, is it still okay to exploit them? Personally I think it's not okay. I think it's a worthy goal to present other options. In an ideal world, perhaps there would be structures in society that define open standards that allow people to find the homogeneous experiences they value while still ensuring that no central authority could take ownership over the delivery of those experiences. Perhaps there should be some assurance that those who deliver the experiences aren't also using other levers at their disposal to engineer the desire for those experiences in the first place.
Which is all to say that perhaps social media should be better regulated, and as nerds we might think that one way to do that is build it into the base technology as decentralization or federation. But one would hope that people outside of tech could at least understand the value, since the tech is just a model of real-world systems.