First and foremost, I want to note that I'm not by any mean "someone", barely knows any mapper and have the perspective of mostly being a player.
So yeah, I don't really understand how "we've regressed". 1 year ago, rules were supposed to be revamped in order to be clearer, due to the whole
El Chivi's song being almost ranked and having extreme profanity in it. They never were. (and the map is still graveyarded, so downloadable)
I have countless examples of maps dealing "intensely" with non-appropriate themes that you quoted being ranked, at any point of time ranging from 2009 to 2017. So I don't see how we could have "regressed", when there never were any rules available for the public to begin with.
Such a subject cannot be enforced or anything, it is too vague, too abstract. There is no one that is fit to discuss which music has "artistic merit" or not. There is too much hurdles preventing that.
For instance, there is the fact that if you want to pinpoint which song is unsafe for 'all-ages', you would need a polyglot or a team of people speaking every single language, as the distinction between being on the grey area and explicitely being violent cannot be caught using a translator (problem of context for each word, for the general song, etc. there are parody songs ranked that are clearly parodical for people speaking the language, non-offensive for people that cannot speak it, but someone learning the language could be confused and think that it's clearly offensive). On the other hand, it is not impossible to write an offensive song without any curse for and with implied stuff, that could be caught only by fluent speakers.
Then, the number of "Pending" or "Graveyarded" maps is too high, nobody can listen to every single one to decide if the song is or isn't offensive. Even the most notorious artists when it comes to being extremely crude and/or violent have done some pretty chill songs, and someone gave you an example on reddit IIRC. And I say that as someone who hates this artist, from the bottom of my heart.
Such hurdles are impossible to overcome, and it's why, IMO, I think that this whole topic is bogus. When it comes to unranked maps, nobody should be silenced, restricted, or even have their maps removed for being in the grey area, as far as the "grey area" can stretch, because under no system it could be fair for all users.
The number of maps passing through the ranked section, however, is drastically lower, and the debate should be up when a bubble or some sort of intense exposure is made (and not before, and not after, as it happened in the past). But even then, a map is bound to slip by at any moment, and it's not really severe, because if the common sense decided that the song weren't offensive enough to trigger a backlash, then it's fine, because it is not likely to shock most users. The number of unranked map is so high, you won't find haphazardly an offensive song.
TL;DR : let people submit whatever they want if it's in the grey area, if the map don't use, and I quote SharpII "excessive profanity/terroristic propaganda/illegal content/screamers". When the map is heading for ranked, then it would be possible to decline the map from there as