I think you overestimate the efforts put into this game. It's just your average Honey Select game. You may like the story, but let's be serious, it's not "well written", even for a porn game. Maybe the developpement of this game is chatotic, so the developper take a lot of time, it seems likely that is the case(hat and the recently health issues). And if the developpement takes time, it's more likely that the developper isn't a developer in the first place, and just learnt for this game (RenPy is pretty easy, it's just some Python and this games doesn't do any fancy things)This game will actually be available for free, once it is finished. And the dev makes every version available for free appr. one month after an beta-update is released. Patroning the game doesn't mean to buy it, it means to contribute to it's development and help the dev to finally finish the game.
If such a game would be available only finished for less than 20$ to buy, we would probably never see only one such complex and well written game like this, as there would be far too few people buying it for rectifying the big amount of time a developer puts in conceiving ideas, building story structure, writing, creating images, adding gamification features and putting it all together in code. This may work for an AAA-game with a millions budget and a big advertisment campaign, that's bought by millions. But probably not for a lewd game, that might be finally bought by some thousands, if at all.
Really, aside from the "base settings", that may fit to your tasting and that's okay, this game is nothing special to any game on this website
And $20 is a big price, see Paradise Lust who is sold for $10 with live 2D renders. Or just any officially translated eroge.