In my limited experience, the "hard problems" in philosophy are the problems which are either poorly defined and so people keep arguing about definitions without admitting it, or poorly analyzed, so people keep mixing decision theory with cognitive science, for example. While the traditional philosophy is good at asking (meta-)questions and noticing broad similarities, it is nearly useless at solving them. When a philosopher tries to honestly analyze a deep question, it usually stops being philosophy and becomes logic, linguistics, decision theory, computer science, physics or something else that qualifies as science. Hence Pearl and Kahneman and Russell, some Wittgenstein, Popper...