Let's just grant you would come to the same conclusions eventually — people that specialised in thinking about metaphysics, ethics, epistemology etc. and spent

Let's just grant you would come to the same conclusions eventually — people that specialised in thinking about metaphysics, ethics, epistemology etc. and spent years writing their arguments in (to a first approximation) well-reasoned prose, which was then subjected to the critiques of their colleagues that followed in subsequent generations who instead wrote their own arguments.. at the very least seems like a huge time saver.