I don't really get the idea of decentralized internet.

The internet is already decentralized. There are millions of websites hosted on thousands of separately-owned machines.

"Decentralized" services like the fediverse use thus exact same structure and bind them together by a search/aggregation API.

The "centralized" part of the internet is DNS, Service providers, and search.

You are perfectly allowed to go your whole life without using search, or by self-hosting searX.

If we go back to the age of webrings, that is essentially decentralized internet. It seems like every decentralized internet idea is just a rehash of this with some Tor ideas sprinkled in.

You are never going to be able to pull a "Silicon Valley" and make every device into a mini server. The ping and uptime would be horrific.