I was taught in university that the "right" solution to the problem of free will (compatibilism) had to wait for a cognitive scientist (specifically, Daniel Dennet).

I am surprised by this. The proto-compatibilism of Aquinas might be little-known, but I thought it was common knowledge that compatibilism has a long pedigree before the late 20th century, including most logical positivists like Ayer and earlier British empiricists like Hume (I would include Spinoza as well). What Dennett gives is a version informed by modern cognitive science, but not especially novel in its basic features.