I feel like a lot of the arguments in this thread are disingenuous... I 100% understand people having their own preferences, people liking what they like, but to call out "The concept is a failure" is incorrect - who is defining success here? Have we checked these game makers patreons to see who is making money and who isn't? Or are a few people in an internet forum deeming something a failure simply because it doesn't cater to their taste?
Niches exist for a reason - for one, Lewd Corner itself exists due to a niche - a broad niche, but "Adult games" is still a niche (and Members+ even more so). Sandbox, visual novel, kinectic novel, 2D Side Scroller, RPGM, games with NTR, all these things that people proclaim ruin a game, only do so subjectively, there is very much still an appeal to someone else out there.
As with almost all mediums in the world - somthing can be good or bad depending on it's implementation, depending on it's concept, depending on it's vision, depending on the passion of it's creator, etc etc. It can be said that there are almost no bad concepts, just bad implementations of them. If a Sandbox has a bad grind - and as someone that plays a lot, I can admit that many many do - it is poor implementation, not a failure of a whole genre.
Also, on the topic of Game Dev itself, Adult Games suffer from being part of a smaller community and, therefore, are often worked on by Solo Devs who can't necessarily advertise their work or work full time on them. Things like "the grind" comes out in playtesting and QA. These Devs don't have access to that. Do we think when games like Final Fantasy get made, the XP grind is perfect from the moment they play it? Of course not, it gets manipulated 100s of times before we see it. It's just a luxury Devs of Adult games don't often have. It's why, in my opinion, VN games are far more prevalent - It's a story, or a glorified choose your own adventure when choices are added (not to do the Devs a disservice, writing a good story/producing the scenes/putting in the time is still HARD and making it a decent game is even harder) - but it doesn't require a Dev to go to the lengths that producing a Sandbox game would - it is exponetially bigger on almost every side.