Piefed allows to block instances at the user level, making defederation less of an issue. You have to keep in mind that there's another part of the Reddit population that prefers to have control over their own experience, and for which having a short defederation list is appealing.
Thriv.social is indeed nice, but they don't provide a lot of details about who the admins are and how long the instance can last. Maybe you can try to reach out to them?
The instance label thing is really minor indeed. You can still probably reach out to the .zip admins about it.
Quokk.au is very Australian focused, I wouldn't use it as a general recommendation.
About Piefed.social, if it reaches 5k active users, then the snowball effect will start and Rimu would have to actively lock it down for new users to spread. I prefer to avoid confusing people by linking to Piefed.social when it might be closed for new users in a few months.