You know, developing a 3D game in Unreal Engine (or unity, or godot) is a daunting task. There are lots and lots of things to do, and the more you develop the more things are added to the to-do list, so it is really difficult to stay true to the commitment.
On top of that, for the majority of nsfw developers, these are first projects and solo projects, so we generally lack the experience and resources to progress fast enough on our projects. Low experience then translate also in major turning back on game mechanics, performance or project scope.
I know, it's frustrating to start a game only to find out that it gets abandoned in a few weeks/months, but it is more frustrating to abandon your own projects, i can assure you.