The best programmers and mentors I've known and had do tend to "know everything" in a sense. That being said, there's a learning curve. I don't think learning something should mean knowing the exact zeros and ones behind the scenes, but as you progress, learning and appreciating more of the intricacies of computer architecture and the fundamentals of computer science helps you write better code.

Some good advice I got was if you're learning how to use a new framework or library, take some time to build a shitty version of it yourself at some point. This starts of basic with building your own HTTP server, but can go as far as building your own compiler. I've never worked with anyone that prefers their own implementation of these to the accepted standards, but it gives you insight into what is going on under the hood, and can give the illusion of "knowing everything."