"Gibberish": Plato, Russell, Penrose and Tegmark?
Made of math is as Aristotle noted: "All is number" — Platonic-Pythagoreanism was at the heart of classical civilization and the enlightenment.
I can only suppose that there is something about these ideas that deeply disturbs or even frightens. But I wouldn't dismiss them as gibberish.
(Also, Platonism does posit an immaterial realm of the forms in which all material things participate. But this participation relation is problematic, something Aristotle pointed out in the Third Man Argument and something Plato himself knew.)