There is a substantial amount of spam and NSFW posts on the All page coming through already. Most NSFW posts aren’t being tagged as such and are coming right through. I am not sure how this can be weathered but we need something in place fairly soon, I feel like we are days away from rivers of bad stuff, especially via some of the federated instances.
EDIT: I personally don’t care much about the NSFW aspect, more in the lines of what a newcomer will be seeing when they get to the main page. 99% of the newcomers don’t know / care about federation and have no idea how to turn that off. Liability for the server owner is also an element of consideration.
You already can mark entire subs as NSFW. I think the problem is that a bunch of folks created subs that weren’t marked as such.
Though with federation, it’s always hard to say just what features other people have. I only personally verified that kbin lets you mark subs as NSFW, but someone told me Lemmy does, too.