Actually, to extend your brick layer analogy, what if that's all you do and we devise drones that can lay bricks really fast? Then what? You're going to have to compete with the other 50,000 unemployed brick layers now looking for welding jobs.
The point is that you spend the time to truly become an expert in an area, most of the skills will be easily transferrable to an orthogonal position. Dabbling in a bunch of crap on the side doesn't really get you anything except for a false sense of confidence that gets blown away when an interviewer asks you any reasonably hard question about it.