Well, when you're just starting out, or trying to break into a new market, the quality of the writing doesn't do anything to snag people in. The presentation and the artwork does. However, when you intend to stay in business for a long time, you can't neglect the writing completely. I have a feeling that a lot of the VNs being pushed out these days are one-ofs, where the devs, for various reasons, wanted to try their hand at it, and won't be coming back. Presentation is everything to these people, because all they'll be selling is that one VN.
If you're in for the long haul, you need a fanbase. This can be built by reaching out to the communities that might be interested and interacting with them, or it can even be created through kickstarters, because those gather like minded people and can create buzz. Other ways exist obviously, but going outside your own circle and publicizing yourself seems pretty important to me. Once you have a large enough fanbase, that in itself will push your future sales through word of mouth, IF what you're creating is of sufficient quality. And here you can't skimp on your writing. "Large enough" is relative of course.
Note that quality of writing doesn't have to be, how good is your story. It can also be, how good are your character interactions. Or how much impact do choices have. How much replay value do you have. As long as you're leaving a lasting impression, and this does require something of quality or one of these hallowed GimmickS.
As an aside, another of the somewhat recent entries into the market is Sunrider, which was crowdfunded, then offered for free. This obviously created interest and a lot of positive reactions, but we'll see if the devs are now able to sell their next game, which carries a much larger price tag. In this particular case, I'm not sure it's left the best impression since the original is not only unfinished, but haven't exactly delivered anything outside of a linear, predictable story and a semi-buggy strategy game (limitations of Renpy). It sure was a good way to get people to play your game though.
Katawa Shoujo is free too, but that WAS a one of, and while complete and fully playable/entertaining, suffers from too many cooks leading to very uneven quality in the writing. It was never meant to be sold, it was a fan creation, by the fans, for the fans, with nobody even having to consider sales.
If I may just push two examples of games that impressed me. Going full Japanese VN, Fate Stay Night was amazing (as I suppose we all know). Incredible length, finishing the game unlocked new routes, collectible game overs, gimmicky stat screens, memorable characters. While it's a pure VN, everything about it screamed quality.
From a western developer, Hanako's Long Live the Queen doesn't have a really long length, but such amazing complexity, replayability and impactful characters/situations that you can keep playing for a long time. Also, collectible game overs (I may have a thing for this). This is a good example of how far you can twist a VN to create something unique.
These are examples of high quality completely by the books, and high quality thinking outside the box, each has their own allure.
Anyway, the simple answer is to create an eroge and watch the sales go through the roof.