Got to remember that this is an amateur based adult/erotic market for most products in this genre of visual novels and games... So there will always be ups and downs... With various factors coming into play that help perpetuate that effect... A lot of the big hitters have been going through development for long periods of time... Perhaps even before sites like Patreon came along... During those moments, we've seen a major influx of very specific fetish focused stories... And because of the Gold Rush commonly referred to as the patron subscription based donation websites, there have been a lot of first timers trying to jump on the coat tails of the more successful big hitters, mostly hoping to get a piece of the Gold Rush pie... But of course with many changes happening, disallowing many of the more risqué fetishes on some of those patron based websites, it is only adding to the up and down effect...
Plus, for a long while there, we had a huge influx of Family Sex stories, most of which either felt like copy cats or were so poorly made, that I think a lot of folks are getting tired of it, and want some more creative ideas... I can't tell you how many first time creators there are, that don't necessarily have the talent for it... Again, it's that diamond in the ruff that happens only every so often... And it's sad when they burn out like a shooting star... Another occurrence that adds to the up and down...
Of course, you will always have some folks who never change, and just want what they want... But the market is made up mostly of people coming and going, wanting all sorts of different things from one moment to the next... Most players/readers of these sorts of VN/Games don't stick around for long once they've gotten their jollies... Most tend to move on to other things, either disillusioned at the plethora of bad starters, or they got what they wanted, and life rolled on... That's how it goes with Porn... There is just so much of it...
I mostly stick around with this genre, hoping to find those few diamonds in the ruff, that present themselves to be more then just common porn... It's a big reason for why I like meaningful and deep stories so much... I don't mind porn fests now and then, especially if they have great stories to mix it up... I'm also an avid novel reader... Heck I was one of those nerds that spent most of their free time during Jr. High and High School hanging about in the libraries or playing table top role playing games with my friends... So, for me, a great story, with well developed characters, to go along with my porn, is a heaven onto itself... I don't want just regular ole masturbating porn all the time... I've seen enough of it over the last 3+ decades to make my head spin... I want something more, something fun, something meaningful, something with meat on it's bones... But I also want it to read good... Hence why I'm so picky about good English, and proofreading, and making sense, and having some partial anchor in reality... It has to be somewhat believable, on some levels, otherwise it ruins the immersion... And immersion is what makes a great story, and makes the porn that much more pleasurable...
Sure, there are those who could care less about all those things, as all they want are sex filled visuals to wack off to... But, if that was all I was after, then I can find literally billions of sexy photos, or porn vids to go watch to get my jollies... I want something with way more to it, then just a bunch of sex pics that are pretty much a dime a dozen...