Earlier quoted context omitted.
Email has solved federation / decentralisation long before WWW. Nobody is confused when you hand them a user@gmail.com, user@hotmail.com, etc; I use my own user@whatever.com and sometimes get a blank stare, until people realise you can go to www.gmail.com to check your own inbox, and you can totally just type www.whatever.com into your browser. Links like reddit.com/u/user, youtube.com/@user, already exist and are de…
It's funny you mention gmail and hotmail. That's exactly my point. Who is setting up their own email server when they could instead sign up for one of those? Is it even 1 in 100,000 email users? (I say this as someone running my own email server, who periodically has problems sending to gmail.)
About the same number of people who set up their own WWW server, modulo the absolute PITA that is email.
Still, federation between GMail, Hotmail, iCloud, Yahoo, ProtonMail, etc does work. You don't have as many choices but it can still feel overwhelming if you're shopping for an alternative. People at Corp & Co use their @corpnco.com addresses daily. My personal email is connected to iCloud, but I can always point my MX elsewhere. Running your own Mastodon instance is costly - however fediverse already leans on smaller interconnecting communities.
Nobody sets up an AS just to run some fiber to their home. Decentralisation and federation just happen at different levels and scales.