Not knowing everything about technology you use is bad
Technology is not an end in itself; it is just one of many means that we humans employ in the project of survival. So even if our goal is only to survive, having an imperfect or limited understanding of technology reduces the value of that technology itself. Everyone knows how to make a wheel. So even if all the wheel-factories in the world were to be destroyed, people could still build their own wheelbarrows and carts. Most people don't understand the science of electricity however. So if there was an apocalyptic event, a few people would be able to generate electricity; most couldn't.
If the project of humanity is more than just survival, then the problem is even greater. Let's say the project of humanity is to optimize human existence. Not just survive, but survive in such a way that individual and social existence is improved as much as possible. Bare minimum, this can only occur if advances in human life are passed forward from generation to generation. However you only use a technology optimally to the extent that you understand it. And you can only pass forward what you understand.
For example, many people think that discovering a source of unlimited, inexpensive power would solve the world's problems (fusion energy). This is naive. All power, when used or applied, ends up as heat. So suddenly increasing power-consumption by an order of magnitude could result in an environmental catastrophe.
Technology can only be used optimally to the extent it is understood. Or to the extent that it's use is directed and controlled by those that really understand it, I guess....