The "replacement" for Nietzsche's books, if that's a goal, must also address WHY Neitzsche's arguments are weak or insufficient. It must also address, to a degree, structuralism/post-structuralism, postmodernism, etc. This is not a process wherein Nietzsche (or Heidegger, or Hegel, or whomever). Questions of "how ought one live?" are not narrowly focused. Simply because you did not study philosophy and seemingly disregard the idea that different people may adhere to different ethical systems (as one part of philosophy) does not invalidate the discipline. There is no universal, provable "right" answer to "what is ethical?" Certainly there is overlap between virtue ethics and utilitarianism and intuitionism for how one might behave, but the reasoning behind them all differs.
Humans are not omniscient. Philosophers are not omniscient. It's disingenuous to talk about general relativity as an example, and much more cogent to talk about theoretical physics (to which I can't speak with any authority except as a lay reader who's aware of multiple theoretical frameworks which cannot be simultaneously true). Sure, you can have "more sophisticated arguments (mathematics)", but the answers to some of these questions may never be known. In philosophy, we will NEVER know the answers to questions about the human condition, the nature of knowledge, etc. Just because it's not mathematics which are "transferable" and can build on top of each other does mean that the knowledge is not transferable or that the arguments do not get more sophisticated.
Exactly what you're describing DOES happen in philosophy, and has always happened.