Choice is not a principle concept of decentralization. In decentralization the only quality that matters is degree of autonomy. If I need your common access point to send/receive content the system is highly centralized as autonomy is fully vested in the third party content host.

The presence of choice only means there are multiple centralized systems not interconnecting.

This is why the web is highly centralized despite choice and why Web3 won’t work. Web3 is focused upon federated solutions. A federated solution is semi-autonomous, less centralized than the web but not fully decentralized.

> In decentralization the only quality that matters is degree of autonomy. If I need your common access point to send/receive content the system is highly centralized as autonomy is fully vested in the third party content host.

Things exist on a spectrum. I have autonomy to choose where to (e.g.) host my family photos, and even self-host on a VPS or even perhaps at home (either with a static IP or dynamic DNS). While things may moved towards more centralization with Big Tech, does not mean it is centralized, just perhaps less decentralized / distributed.

> multiple centralized systems

This phrase approaches an oxymoron in my mind. (Bearing in mind de/centralization being on a spectrum.)

Earth has multiple governments. Most governments are highly centralized. No oxymoron.

Autonomy is the ease with which people are free to move between those governments.

I suspect people view the web as decentralized because they cannot divorce their thinking from concepts like content is king and a client/server model.

> Earth has multiple governments. Most governments are highly centralized. No oxymoron.

But you wouldn't say that the governing of Earth in total is centralized (e.g., the UN (with their black helicopters/s)).

Going back to my link:

> As its name implies, decentralized systems don’t have one central owner. Instead, they use multiple central owners, each of which usually stores a copy of the resources users can access.

> A decentralized system can be just as vulnerable to crashes as a centralized one. However, it is by design more tolerant to faults. That’s because when one or more central owners or servers fail, the others can continue to provide data access to users.

* https://berty.tech/blog/decentralized-distributed-centralize...

Or Baran (1964):

> For example, type (b) in Fig. 1 shows the hierarchical structure of a set of stars connected to the form of a larger star with an additional link forming a loop. Such a network is sometimes called a "decentralized" network, because complete reliance upon a single point is not always required.

* https://www.rand.org/content/dam/rand/pubs/research_memorand...

You are confusing terms. Centralization is a noun describing a verb, centralize, which means to come towards a collective center, for example a cult. The verb, the action, has nothing to do with a philosophical concept of a total center.