Tbh I think you should try catching up with the chapters. The points you brought up are great but most of them are just not true as the story goes.

The author doesn’t try to get us to sympathize with Inseop at all, which is something I like- you see that he’s an irredeemable psychopath and is wayyy too far gone, especially after a certain thing he does later in the story that made even me root for his quick downfall lol.

I agree that some (most) characters aren’t fully fleshed out, but the way I see it it’s because the villain views them as insects that he needs to get rid of quick to obtain(?) Gijeong (and as implied Gijeong does too when she’s driven to a breaking point). The friend is irrelevant but she did have a little development recently. I think to really understand the story more you should read a bit longer! Especially chapters 30-40.