Since the onset of the dot com explosion of the mid-90s, the internet as it exists today has existed upon a centralized framework. The metaverse and NFTs are aiming to change that.
When considering the centralized web, or Web 2.0, think of it as a series of privately owned office spaces within a large building. Companies like Facebook, Google, Amazon, and other mega conglomerates own pieces of this infrastructure as a whole.
These servers are privately owned. Therefore, the information they allow on their networks is centralized and subject to permissions. These control the flow of content and subscription base based on terms of service agreements between the users and the services offered by the providers.