Neat! I haven't heard of some of these, so this seems like an interesting thread.
I mostly agree with the point about the burden of expectations and game scope, and the painting metaphor is apt. Too many artists (and especially game devs) try to make a perfect masterpiece rather than being content with finishing something pretty good. I'm not familiar with Seth Black or Shiny Dev, though. Who are they? Excuse my ignorance.
-At the moment, the game I'm most anticipating but also worried about is Tame it Too. It's been in development for a few years now with no release date. Light-hearted ero games that aren't VNs are pretty rare, so it would be a shame if it were dropped.
-Another one is Neon Nites, the sequel to Third Crisis. It was well publicized and just released into early access on Steam a few days ago, but I'm afraid that the new policies combined with its relatively high profile might get it taken down. In some ways, the big releases are the most vulnerable to censorship.
-I also have a bunch of old games I've been following that either get a small update about once a decade, or have no hope of release whatsoever. Like, I wish Alder's Fall of Eden would get finished some day, but it's been abandoned for years now at this point. Wape's Incbus Island also comes to mind as a particularly anticipated release, but I think it was confirmed as abandoned. And there are too many others for me to even attempt to list here.
As for why games get abandoned, well, other than audience pressure and the impact of censorship, I think a lot of 18+ games get dropped or slow to a crawl simply because real life intervenes in some way. Most ero game devs are hobbyists (at least outside of Japan), and sometimes people either lose interest in their hobbies or just have too many other responsibilities. A good example would be the Free Cities dev--I remember reading that he got some kind of promotion at work and stopped developing his game as a result.
Other devs quit after realizing that the amount of time and labor it would take to finish a project might be more than they can spare, or the project has gotten out of the scope of a solo dev. Some bite off more than they can chew anyway and spend years working on a magnum opis that will be never finished. I rather suspect this may be what happened to the Teraurge dev. Lilith's Throne would be another example of a game suffering from overreach and ambition, although I'm still hopeful it may be finished some day.
Then there are financial schenagins and personal drama between devs, of course. (Anyone remember the Breeding Season debacle?)
Some artists also just decide to stop making porn, or become disgusted or disatisfied with their own work. You know, like some hentai artists who vanish overnight after deleting all their works.
Time also has an impact. A lot of the old Japanese and Korean flash circles I remember from the early 2000s no longer have working websites, and seem to have retired or gone into "legit" game development. The same goes for a lot of flash-era furry artists. Mittsies, for instance, who some may remember fondly for his lewd MLP flash games, now mostly just does music, last I heard. And Kittery (of Paraphore fame) seems to have distanced herself from extreme porn writing after parting ways with FallowWing over creative differences, I guess.
And some devs and hentai artists who vanished may just have quietly passed away without anyone finding out about their secret hobby or at least making an effort to keep their sites alive. (On that note, I worry about certain Eastern European game devs who went silent a few years ago, after the "special military operations" started. I hope nothing bad happened to them.)
