The character designs have become outdated over the years.
There are already many games in which the characters look more attractive and natural.
That's kind of true. I would argue that Milfy City's character are still pretty damn good, especially for their age. But it's true that since the game has received basically no significant updates in more than two years, there is another, growing problem:
When you abandon a project for so long, even if you want to come back to it, it becomes more and more difficult to pick up where you left off, since softwares, tools, methods and so on upgrade and change over time. That means your renders will look substantially different, maybe some characters or specific tools aren't supported anymore, etc...
But the art style especially will begin slowly to look outdated, because you still have to use the same render parameters and techniques from 3-4 years ago when this game was initially created, unless you just use new parameters but then the new updates will look substantially different from the old ones, which may break the experience.
That's why you need to keep realistic development and lifespan time. Creating a lewd game over a period of 4-5+ years is bound to create a LOT of problems.
But that also wouldn't have been too much of an issue if ICSTOR wasn't a massive scammer that knowingly and purposely extended news update in order to milk the absolute shit out of clueless first-time pledgers.