Wish you could have a route wherein you can be in a relationship with anyone except D without getting a "game over". Dating My Daughter doesnt have to be literally as if romanctically abnormal between Father and daughter. Like in the early parts of the game, they called it "dating" as in friendly family bonding only. Why cant we have that?
Why cant I have Margo or Georgina to myself without love points on D?
(assuming this isn't a troll comment....)
Because development time is a finite resource. This is a niche game for a particular fetish. Having the developers devote time away from that particular specialization in order to support other interests might broaden the appeal somewhat, but it will also reduce the amount of content delivered to the core (i.e. paying) audience.
Specialization is a thing. Fro a lot of people, it makes more sense for one game to have a ton of incest content and another game to have a ton of (for example) milf content than for both of them to half-ass both kinds of content.
In the case of DMD, because it has been drawn out for a truly remarkable amount of time (an why not? It is making money, and the fans are enjoying it) lots of other niches have drifted in there-- some vanilla, some interracial, a bit of yuri, a bit of loli, some milf, etc-- some of which has attracted guys like you. However, if you expect the level of non-incest content to be anywhere near the level of the core content, you are going to be disappointed. You're better off looking into other games that *do* specialize in those areas.