This statement is not only largely subjective, but also incredibly confusing.
Question: who's going to slog through a 15-25 hour long story just to see a naked picture of a male or female? Answer: no one becuase we could all just go look that up on the Internet.
Secondly, ,any vns have fantastic stories, well thought out universes and characters. Again, that is a largely subjective statement , but people don't buy things, and things don't become popular becuase they are bad. There are of course some out liers but I really don't think you're giving vn writers a fairs shake here.
Note: that's not to say there aren't a lot of bad vns, but there are also a hell of a lot of bad games, bookes, movies and songs also. Every medium has its stinkers.