I don't know any place which have the proposed "soft nsfw" filter separate from "nsfw".
Comparison with reddit is weird as reddit r/all is full of ""artistic"" pictures or paintings of naked women.
Also the fediverse is not really like reddit. The more the platform grows the more useless All becomes. Try to go to mastodon and browse by "all" it's unusable. Either pick an instance with a good "local" you like or all is not really that important. I don't think it's a "first impressions", first impression is "local". All is never going to be a curated feed, not a consistent one. It's a federated platform, which means a LOT of diversity and variety on communities and posts.
Also I don't see or even want to start consider anything that shows a little skin "nsfw". I think that's a very personal taste that should not be universally applied.
I really don't buy the argument here.