In the middle means that you have a large number of small centralized services that are interoperable. That way you get most of the benefits of centralization e

In the middle means that you have a large number of small centralized services that are interoperable. That way you get most of the benefits of centralization e.g. someone else manages the technical details, you benefit from the network effects of the service, the service can provide things at scale that you can't on your own and you get most of the benefits of decentralization e.g. you get to choose a service that is more in alignment with your principles, has the bucket of features you prefer, has the community you want to interact with, you can switch to a new service whenever you like. You also have to lose something in exchange, you can't fully customize everything the way you like and not everyone in the world will have exactly the same features available to them. It's a compromise. The key to making it work is having a common protocol and everyone agreeing to at least speak to each other rather than building their own walled garden Utopia™.