mine is perhaps a mastodon with dislikes
a loops like but for youtube shorts instead of tiktok
email (i am not technical but since it is hard to self host email what if someone made a email that could be self hosted that is a part of the fediverse)
and a facebook like that isnt outdated as friendica
The problem isn’t a lack of plugins. Email servers have all sorts of “plugins”. Any spammer prevention plugin you can think of, and a thousand others that you haven’t even imagined have already been implemented for email.
And email servers already defederate all the time. That’s why it is hard to get small email servers to reliably send mail. You have to convince others to federate with you.