What is even the point of studying Aristotle in this day and age? How can his metaphysics, ethics, etc. have any merit when they derive from his empirically false observation of physics?

What does Aristotle mean by "substance" (ousia)? How does he distinguish between primary and secondary substances? Why are individual, concrete things (like "Socrates" or "this tree") considered primary substances, while species and genera ("human" or "animal") are secondary?

When studying logic several materials/sources talk about a difference between arguments and explanations. However they all suck at explaining this difference. How come? Is this some modern shit perhaps?