The Slice website is merely an interface for interacting with its contracts on Ethereum. Just this fact has profound implications on ownership and privacy, and makes it hard to compare it with any centralised service.

True ownership means that no-one can ever stop you from selling content, or earn from it. It also comes with the freedom of selling part of your ownership to others.

It introduces the concept of NFTs with objective value (based on slicer accumulated ETH) which makes it possible to leverage the unique characteristics of web3 and NFTs in real world applications.

Composability makes it possible to seamlessly combine Slice with any other contract or web3 service. This is the case for example for Slice used as tool to handle payments to DAOs, or to establish temporary project based on collaborations between DAOs and individuals.

I agree that at first sight it may seem like it introduces unneeded complications with respect to traditional centralised services (especially from a customer's perspective), but comparing Slice to existing marketplaces doesn't really have sense as it effectively represents a new way of owning, creating and selling content.