Exactly. I managed to ride a nice maybe 8 year wave as an "OpenGL expert" but the industry moved on and I didn't go more general with 3D graphics to climb out of my niche. I haven't been in that industry since the OpenGL waterline crested and went back out to sea. Learned that lesson.

Be a generalist. Yes, deep specialists exist and yes, some of them have successful careers based on their deep specialty, but betting on specialization is like a high school kid planning to be a MLB baseball player.