I think this is actually related to why Steam's market is such crap.
See, the market for Japanese eroge has been around for a LOT longer, so the people making the games are often 2nd or even 3rd or 4th generation devs. They have plenty of material to study from and a lot of "senpai" to tell them what does and doesn't work. This has the unfortunate effect of a lot of DLsite games being functional but rather lacking in variety, but if you just want a good ol' fap it works fine. Japan is also a bit more consistent with what is and isn't allowed where when it comes to adult material. (they're really not when it comes to the written letter of the law but the unspoken rules are pretty consistent once you learn them)
By contrast the non-Japanese market is rather new, with some entire COUNTRIES barely familiar with the concept of porn games at all, let alone ones that are functional. Western devs are also more wont to violate the "If it ain't broke don't fix it" rule and try to make their indy basement game more ambitious than it needs to be.
As a pretty solid example, there's a Japanese indie game dev named fume that has churned out two HUGE games over the course of a few years. They're not very innovative games, and are almost exactly the same mechanically, but they do the job and aren't completely terrible (the MTL translation of the second game is terrible but honestly this game's word count is so absurd it'd probably take a year to translate properly).
By contrast game devs in the west with the same number of people working on them can't even finish ONE game in that time because they keep adding pointless shit to the first without taking a step back and saying "maybe I should focus on this game working right and save this Cool Thing (tm) for a new project". I follow like 3 different games that have been in development for 4 years and still only have 2 or 3 of 5+ planned chapters finished because they keep getting bogged down.
And Steam is where the half-assed betas of these games end up when the developer realizes they're hemorrhaging Patrons due to a combination of Patreon's policies and people frustrated at the lack of updates.
So it's a self-perpetuating problem until someone makes a true golden goose porn game that takes off. But to do that they need to stop fucking around and get it fucking down. So to speak.
