Because those things are morally wrong in reality, but not in these games. Even games where there is corruption, as long as the narrative reinforces a positive and better situation, it's good.This explanation makes it very concerning that you are fine with the harem, incest, and shota parts of it.
What is your real life like my dude?
For example, there are games where the MC is a deviant that creeps on his family and manipulates them for his gains. These games are NOT games I like to play much anymore. The games I typically tolerate for example have to have a healthy take on with happy relationships. The tags you mentioned aren't moral things that can EVER be okay in Real life. However, in a game world or literature, the writer can paint the canvas however they want. Incest in particular can be orchestrated to be both consensual and wholesome and can skip the power dynamics issue the real world has.
One of the reasons why I like writing is cause I can bring to life things that can never happen in real life. One of those being happy, healthy and wholesome incest threesomes Mind, my game doesn't have that, but maybe in the future