IMO a better general solution is UUIDs and a petname system, at least as far as chat apps are concerned.

For buckets I thought easy to use names was a key feature in most cases. Otherwise why not assign randomly generated single use names? But now that they're adding a namespace that incorporates the account name - an unwieldy numeric ID - I don't understand.

In the case of buckets isn't it better to use your own domain anyway?

Having worked in this space for years, it's not nearly as bad as you think. IaC tools can all look up the accountId/region for the current execution context and you can use SSM Parameters to give you a helpful alias in your code.

Also, if you have a bunch of accounts, it's far easier for troubleshooting that the accountId is in the name: "I can't access bucket 'foo'" vs. "I can't access bucket 'foo-12345678901'"