"Just running your own server" is the proper meaning of "decentralized" [0].
Urbit has a literal operating system named Arvo built on top of a virtual machine named Nock. The terms are used technically; it's not trying to compete with Windows.
That article goes straight into peer-to-peer and file sharing so it is hardly surprising that most people expect a decentralized platform to exist primarily to eliminate SPOFs, i.e. provide redundant access to data of down peers.