Perhaps those were the most efficient jokes?

Lemmy is basically just a decentralized clone of reddit. A public profile containing comments, posts, upvotes, and the like are considered an integral part of the Reddit experience. I personally don't like it as a feature, but that's why it exists.

They're private in the sense that there isn't a corporation stealing your data without your knowledge, selling it without your consent, whoring you out for ads against your will, and/or making your experience shittier to manipulate you into buying their paid features. These alternatives offer a much more pure experience for the typical user. Things like comment and vote history being public is just a part of the design of the forum, they're not tools to farm your data.

That's also true, but I find the ability to decide what gets blocked and what doesn't to be useful sometimes

Turn it on them. Ask them to give up something private in front of you like their phone or wallet. Hey, if they have nothing to hide then they shouldn't worry... But they will.

Mastadon, Searx, Fediverse, and so on aren't killing or replacing the sites they're modeled after, not even close. They're just providing a privacy focused alternative for those who don't want to whored out by corporations or abused by powermods or shitty business decisions