I'm sick of these manga adaptations of novels that all look the same. Is it some kind of obsession among authors to systematically create a naive and weak main character who becomes a cheat and has a harem?
It's escapist slop for bulled, outsider, possibly incel kids who have nothing better in their lives. They get to watch a character who gets universally crapped on (just like they think they are) and then live vicariously through that character rising up and getting the karmic reward of a throng of shallow, easy girls throwing themselves at him for no good reason other than that he's kind of pathetic and maybe generically "nice" in spite of all the abuse heaped on him.
That's all it is. Japan has a huge issue with bullying, power dynamic abuse, and "the nail that sticks up gets hammered down" being used as an excuse to guilt people into not addressing their problems if that might inconvenience or reflect badly on others, so rather than address it they basically medicate it through trash stories like this.
Sometimes, almost by accident, those stories end up decent. But lots of the time they just end up being generic, lazy, ass storytelling garbage that offers nothing of consequence because it's just junk like this.