There is a big difference between mild NSFW and full on porno. Suppose there is a News story with photo/video but it's a little bit graphic or violent. Nobody is jacking off to that. Maybe shouldn't view it at work, but in the library is fine.
Maybe it's a funny meme pic but there's a nip slip situation going on. No biggy; it should probably be tagged NSFW. Probably don't want it showing up at actual work. But I want to enable this kind of content away from work without a bunch of actual porn showing up in my feed.
There should be a porn tag. It's not the same as NSFW.
EDIT: The two main devs have done some amazing work here, but as I understand it they are totally booked for the foreseeable future. My rust chops aren't quite up to snuff (yet) and my frontend chops are non-existent, so it might be a quite while before I'm up to speed enough to make a meaningful contribution. In the meantime just thought I'd point out the issue.
I agree that the de-federation and attitude is worrysome, but I disagree on your stance towards more tags. Servers that disallow NSFW now, might choose to allow NSFW but not porn. Servers that allow NSFW now, are likely to keep allowing both. Servers just don't want to deal with liability and weird protocol quirks showing people stuff they don't want, so they'll ban any category that's likely to include stuff they don't want. More fine-grained tagging means they can ban a smaller selection of things.
I'm all for various kinds of tags to indicate why someone might not want to view certain content.