So I've got a gut feeling that math (like human languages (like programming languages)) is best learned in service of some greater end. I look at some truly impressive projects like CLASP which sprang into existence not because of someone noodling around, but because they had a bigger goal which required the team build it. So my advice to any mathematician who feels lost, like they don't know what to work on, would b…
Far from being motivated by some applications, the most useful discoveries in mathematics are usually discovered "for their own sake" and their application is only discovered later. Sometimes centuries later!