Sorry, but why can’t a complex invention be covered in part by patents and in part by trade secret and maybe some other parts of it is just public domain knowle

Sorry, but why can’t a complex invention be covered in part by patents and in part by trade secret and maybe some other parts of it is just public domain knowledge? I understand you are attempting to make a moral argument and not a legal one, but I’m not seeing your position because I don’t understand from what you have commentated so far why this is immoral.