I disagree with porn having no place on the Fediverse. A lot of amateur creators started their work on sites like Reddit, and the platform becoming unviable will push them to alternatives like Lemmy.
However I do agree that there should be some gateways to get to that point. Filtering instances/subcommunities that are marked directly as all-NSFW is a good first step (and should've been part of the protocol from day 1).
I also see why the default "filter out all NSFW content" filter is problematic (even though it is enforced by app stores on every mobile platform, sadly). A much better approach is to filter subcommunities and instances that are marked as entirely NSFW. That way e.g. news subcommunities can still post NSFW articles that have a wider reach, without anyone's primary feed getting slammed with porn and gore.