The simple fact of the matter is, the Fediverse is public. It’s a space specifically built on sharing.

You're thinking about it wrong, a good blocking system doesn't need to hide the content but rather block interaction from the offending user, like a softer form of a ban, but only for that specific user. They can still see all content from the user but they just aren't allowed to interact anymore. Could they bypass it with alt accounts? Yes but they can also bypass bans as well using that same method, so it's not a good argument against something like that.