All depends very much on the instance you are in. Depending on who the people in your instance subscribe to, is what is shown in all. I didnt have much porn between .ca or reddthat yesterday. It also depends on how you sort in that instance.
I checked on the All feed, both under New and Active. It took me several pages of browsing to find a single pornographic submission, and to be honest all you really have to do is go into settings and either disable NSFW content or block communities which post porn. Only like... two or three NSFW communities on LemmyNSFW are really hitting the All feed.