nobody understands fully how computers work

I mean, tap the breaks a little bit, here. “Fully” is doing a lot of lifting.

I will concede most people don’t understand the concept of transistors, much less the electrical engineering that turns a series of transistors into a CPU. And I’ll spot you that - for any given computer - it would take multiple extended papers to explain every piece of functionality.

But - broadly speaking - if you a computer engineer, you understand how a computer is engineered. If you’re working in IT, you have enough of a functional knowledge that you can tell what each general component does. And if you’re a full stack developer (rather than someone who just does business logic on the backend), you should have a generalized understanding of client versus server versus database and how these pieces fit together. You should also probably have some grasp of the network stack, if for no other reason than you occasionally need to troubleshoot it.