I’m a tech nerd and software engineer and even I struggled to figure out how to signup. Most people I know just want something that works. And those things tend to be centralized because of ease of use. The Fediverse isn’t easy to use, and makes the user make major decisions before even signing up or understanding the tech.
Eventually there should probably be account migration and a somewhat “central” account management instance that most users are on, with the option to migrate their user to other instances.