> I've been a software developer for decades and I get to solve new and (what I find) interesting problems on a fairly regular basis. Most of that problem solving involves thinking; with a minor bit of doing at the end

Great answer overall, but this bit specifically is so crucial to maintaining interest long-term. Mechanistic programming needs to be done sometimes, and it's every junior's first impulse when presented with what they think has an obvious solution (see the problem -> start coding, or "why don't we just refactor this? I'll just put in a ton of extra unpaid hours and make everything better"), but that wears thin very quickly to the point of risking burnout.

You need to develop perspective on why you do something and what impact it may or may not have on small or large scales, and put yourself in positions where the majority of your labor goes to understanding how to apply your skills or resources in a sufficient way, given the constraints in front of you and down the line; this isn't just to advance your measurable skills or your resume, but to maintain your interest in what can quickly become incredibly dull and soul-sucking.