*nods*The thing which makes Type-Moon VNs stand out among the vast ocean of the Japanese VN market is that the character development in their stories is unlike most of the published ones out there. It's deep, dark, and the universe TM created is equally complex.
You hit the nail on the head - at least for me, anyway.
I've known about the existence of the stereotypical "fluff" VNs for years. But it wasn't until I came across Type-Moon's work that I was convinced that VNs could be a reasonable media through which a compelling story could be told.
I also have to wonder if there's a lack of OELVNs that focus on the light, happy-go-lucky dating sims because, well...There's already a boatload available from Japan. Why compete with a really prolific competitor? I suspect people working on OELVNs are shooting for more unexploited genres - underrepresented genres.