as long as (a) these subreddits moderate the content to remove generations depicting real people, and (b) the subreddits are marked as NSFW with the usual "I am 18+" acknowledgement to enter, I don't see why the subreddits need to be shut down entirely.

Reddit has long stopped caring about being reasonable when it comes to subreddit bans. Their policy now is to just stay well on the safe side with things like this.