As we learn more, I agree that higher level approaches will certainly find application. But to the idea of creating industrially useful quantities of spider silk, what's really going on is engineering an entire production workflow. For example, we've heavily selectively bred Bombyx silkworms, to the point that they are true domesticates: they cannot survive (or even eat) without direct human maintenance. (Note: there are many varieties of wild silkworms as well, many tended for fiber use.) This is incredibly labor intensive, and the fact that we continue to do this speaks to the high value placed on silk. We could engineer another domesticate biofactory as a spider, but that seems likely to also be incredibly labor intensive. But who knows, maybe an arachnid equivalent of Bombyx mori could spawn an entire spider silk industry?

Still, the desire to use bacteria as protein factories holds obvious allure for industrial scaling. Of course, that means we need to engineer not just protein secretion but the entire process from gland to spinneret.