I think it really is just a preference thing at the end of the day. Koikatsu tends to be viewed least favorably out of the main three (those being Daz, Honey Select, and Koikatsu). A lot of the most successful Koikatsu games sort of pale in comparison to the big Daz/HS games in terms of support. You used the term "Koikatsu weebs" yourself and I wouldn't be surprised if that's a popular mentality. It's very anime style in general and a good amount of devs play into it, so maybe the majority just isn't into that? Couldn't tell you for sure, more speaking as someone who's just been around the site for a bit.
I would not count myself as a Koikatsu superfan, but I don't really have a preference in the first place. To me it's more about what a dev does with it. I've played great games from all three of them, and at the same time have played a lot of stinkers from all three of them. In this case, I think this game is great and is very different from the usual. I haven't played the newest update (letting them build up so I can binge), but out of the hundreds of AVNs I've played this one has been shaping up into a favorite of mine.
Edit: To add onto the topic a little more, I don't think the $450 the game is currently making is necessarily bad either. This has been around for over a year and in that time has gotten 6 releases including the first one. And yeah, there was a 7 month? time span between v.05 and v0.6 as well. Not to bash the dev for that, is what it is, but visibility is only really getting boosted when updates drop. I haven't done the research to back this claim up, but I have a feeling if the releases stayed consistent at about every other month this might have a bit more popularity/support. I do hope to see this reach the level of those other Koikatsu games at the least though, and I have some confidence it can get there.