High school physicists are not ploughing through Principia Mathematica, instead they learn the laws of motion and move on. Physicists pretty much leave behind the original sources until you are at the bleeding edge. Why can't philosophy?
Sometimes, however, they do borrow eachother's tools at least.
until it's not, at which point it moves out of the domain of Philosophy and into physics, math, psychology, what have you.
(No, the "philosophical atoms" of Democritus weren't atoms as we now know them. For one thing, the word "atom" means "uncuttable", as Democritus imagined atoms to be the indivisible units of matter, and, more importantly, he had no larger experimental and explanatory framework to slot his ideas into, so he couldn't come up with ideas like molecules and chemistry that, to us, follow quite naturally from the notion matter is made of atoms.)
And philosophers DO consult the original sources. Those would be basic logic and rhetoric. Then they take those and they first build epistemology. Then they use that epistemology to build a framework of metaphysics. Eventually they build the most abstract, highest level piece - ethics. At each step there are varying options, and it is rare that you can point to any of the options as 'clearly true'.
We already know mathematics and similar cannot address everything. A 3-body system of perfect sphere interacting solely under universal gravitation is already in itself so sensitive to initial conditions that the error on any prediction you make grows faster than anything computable. So how is humanity to deal with things that happen on the scale of trillions of trillions of entities interacting in non-linear ways constantly? That's the world we actually live in, and the tools to address it won't come from math. And probably not physics (although maybe).