I’m not sure you understand what decentralized means.

You’re perfectly free to go on Lemmy instances that don’t have that as a rule.

How can you have been on Lemmy longer than me yet have such a fundamental misunderstanding of centralized/non-federated vs decentralized/federated?

Here we go. If let’s just say all the instances came together and did the same ban because some hivemind mentality had taken over. It would metaphorically be centralized again. The chances of that happening-probably zero.