The Philosopher: A History in Six Types, by Justin E. H. Smith

"Philosophy has thus become whatever it is that philosophers do." Similar to "Musical compositions have thus become whatever it is that composers of music write."

Nope. I appreciate you want to reduce Smith's point to a tautology, but it is more like 'great music' has become whatever is popular on YouTube. The thing about 'real' philosophy is that it is applied to something - from social justice to fine art or whatever. The people in universities who study the study of philosophy are not doing philosophy in the required sense.