It's true that
Dumb Koala Games' stories are usually quite short - but I don't think that's necessarily a bad thing.
Far too many games these days - both the smutty ones and in general - are just far too long, especially if they feature boring grind mechanics that are meant to artificially stretch the playtime.
I'd rather read a short and crisp story than a long and boring one - but that's ultimately personal preference.
The problem here is quite simply that lesbian games are clearly a niche game market - and lesbian games with incest are the niche of the niche, so the offer here is extremely limited (at least among western productions - maybe it's different on the Japanese market).