Let's be realistic and not hope for a bright future and other stuff that you have in your head and accept reality.
These are porn games and their task is to fulfill a simple and understandable concept, to give the game entertaining content with a minimum of infuriating mechanics for adult games with sex content. A good story and gameplay is a nice bonus that a game of this genre can give, but it's not the main thing, the focus is on content and more content!
Why? Yes, because there are enough games with a plot and gameplay. But porn games with a lot of content are rare, and the authors are trying to sit on 2 chairs and as a result? It turns out that the game seems to have content and normal gameplay, and God forbid it was done with good implementations, usually grindfest.
Thus, most games are similar to each other. As they say, why try something unique if there is a working scheme.