Typically, philosophers do whatever they want and label it 'philosophy', and will claim most positive historical figures as examples of 'philosophers'. Symetrically, those who are skeptical of the value of philosophy will note that anyone who does anything useful couldn't possibly be doing philosophy, sometimes "by definition".

Definitely true, and this suggests that the question of whether philosophy is good/bad/useful is fundamentally confused. One definition that I like is that philosophy is any academic study not otherwise classified. That explains why there are so many examples of fields starting out as philosophy, being given a classification and then not being philosophy any more. It also makes most attempts to say things about philosophy as a whole look rather silly. The only problem with this definition is that a few fields, like ethics, have classifications of their own but are too narrow to count as separate fields, so they're classified as subfields. Still, I think that this definition does a good enough job of dissolving silly questions that we can ignore a few special cases.