Valuable advice. I've found the same w.r.t. working at a small company versus an enterprise. I think I'm in the niche carving stage of my career but I have no idea how to sell myself. I'm in the same boat, I can and do operate across that wide swathe of experience as well.
It's been feeling lately like I'm at a crossroads, I either settle down and "specialize" by picking a stack and an "area," or I build my own product.