First, I disagree with you regarding Melody. In terms of story structure, character architecture, etc, it has way more originality than 95% OG the other games out there. If you are considering only physical sex actions done as originality, then you are right. But then a variety of sex actions In itself is not particularly creative and original - it is the weaving of them in as part of an organic character/plot driven story that makes them creative and original.
As for “success [of Melody] is far less behind [DMD]” - if you take f95 posts, then you are correct; if you take number of Patrons, then you are incorrect (though they had/have a difference of @ 200 Patrons I believe.)
As for MDots staff support in bestiality, one person discussed it with D (or hinted at it in a wishlist); there was discussion by another of it with Frank’s sister (kind of a punishment event); and I have been against it with D but okay with others. Have no idea where MDots stands on this as I never asked him.
I do know that (in this VN) incest has become SO much more normalized in this VN world compared to the real world. Take the male characters that have had more than one scene - three of them (MC, Jeff, and Olivia’s Dad) have hand incest. Add in that the only stated reason for a frowning on incest in this world is the view of society. There has not been, and probably won’t be, a discussion of genetic abnormalities in this VN as a reason against incest - imo in this world incest does not cause genetic issues. Instead, imo the societal issues revolve around the issue of parents being in a position of trust, so that incest with a daughter and a step or adopted daughter have the same weight.
We might still have beastiality yet, but I doubt it will be with D. D still has to work thru the following that have been hinted at through various means:
1 - anal
2 - rimming
3 - accept creampie - accept possible pregnancy
4 - marriage to MC
5 - threesome with Elena - Elena as housemate and MC’s sex partner
6 - accept Georgina/Jennifer as MC’s sex partners (and housemates, etc)
7 - accept swap with Margo
8 - whatever might come out of the hinted Rachel storyline
9 - whatever might come out of the Cassandra storyline
10 - whatever might come out of Martin storyline
11 - BDSM
12 - nude (and sexual) photography for someone other than MC
Given these probably have priority over D and incest, and the format is to work D thru each step in her character development, and DMD in this format is finite, imo D will not get to beastiality.