Well, let's start with your first argument, No, the most popular adult games don't have an MC with a super big dick/hyper etc, Hyper and all that is a very niche fetish, if you look at the top seller games in the NSFW tag in this website you'll see that none of them have an MC with a ridiculous dong, same happens in F95 an even bigger website for NSFW games, probably the most popular website.
2nd, Twisted World is not the most popular Koikatsu game, there's plenty more popular like Corrupted Kingdoms (4,456 Patreons and 15.7M views in F95) or Hero's Harem Guild (1,293) and in both of those games the MC does not have a massive dong, in fact all characters in those games have proportionally correct bodies, which is probably the reason why they are so popular, the characters are attarctive/pleasing to the eye.
3rd, Futanari is an already a niche fetish, Hyper is an even much more smaller niche, what happens if you combine them? you get a super niche game that not many poeple will want to play and even less will want to donate to, let's remember that Hyper is considered one of the "gross" kinks for many people, if you were to combine Futa with Hyper you are basically shooting yourself in the foot by further limiting your playerbase and thus your potential source of income, if you go look at F95 and search for the Futa tag and order by views or likes you'll see that games were the futa has a massive dong are nowhere to be seen in the first pages, in fact you have to dig a lot to find those, yes Summertime Saga is up there but the "futa" in that game has a normal dick, maybe even below average lol.
In short I think this game has a bigger chance at attracting more poeple and getting more support if it keeps going down the current path, the character models are really good, it's clear that time and effort was put into making them look good and stand out from your average Koikatsu game, there is a good sense of proportion and anatomy which does wonders for them already but the faces and hair also look good, the "assests" aren't too exaggerated as well which as I already said helps in making them look good, I really hope the dev keeps the characters like this and that future characters also have this level of quality and effort put into them, so far the game has super good potential thanks to the characters alone, but I will say that the story so far and writing has also been really good, which is why it was able to turn so many heads with the first release already.