Mathematicians have thus achieved the ultimate philosopher's dream
Plato agreed, which is why he held up geometry as the standard for judging other "sciences".
And much later, it was shown that the geometric "truths" that were settled questions do not describe the physical world as had been settled. Indeed, it turned out that there are many geometries other than Euclidean geometry. Solved problems need not stay solved, even in mathematics.
Philosophy is notorious for not answering the questions it tackles. Plato posed most of the central questions more than two millennia ago, and philosophers still haven't come to much consensus about them. Or at least, whenever philosophical questions begin to admit of answers, we start calling them scientific questions. (Astronomy, physics, chemistry, biology, and psychology all began as branches of philosophy.)
A common attitude on Less Wrong is "Too slow! Solve the problem and move on." The free will sequence argues that the free will problem has been solved.
I, for one, am bold enough to claim that some philosophical problems have been solved. Here they are: