Default instance blocks should largely replace defederation
Since what content users might want to see is quite unlikely to match which servers the admins tolerate, choosing instance on the Fediverse can be quite complicated, which is inconvenient and off-putting for new users.
For this reason, and simply that the Fediverse is stronger united, I believe defederation should ideally be reserved for illegal content and extreme cases. If Fediverse platforms would allow instances to simply block the rest for users by default, the user experience would be the same, unless they decide otherwise.
The health of the Fediverse depends on individual admins. Would you say that the Fediverse is unhealthy right now, because, for instance, beehaw.org is defederated from some communities, but you’d like to see them? I wouldn’t agree with that. You can always join them and see the content that you like. That’s the whole point of having different instances.
I just thought the entire point of the Fediverse was kind of the ability to access any content, regardless where you choose to be. This is not only directly complicated by defederation, it also adds a whole new layer of complexity for new users, for whom this idea of decentalisation is already quite off-putting.