I think that goes for beginners; experienced programmers have a lot of ideas about how they might work.
I, for myself, have written a lot of “vanilla” code. I know how to communicate with SQL and NoSQL servers, cache systems, and a lot more. I know how to handle Web requests, command line options, environment variables, I can manipulate memory and files pretty effectively. I know how the operating system works behind the scene. Heck, I even know how bits are flipped in memory modules and disks.
Bragging aside, if you have seen a lot, you probably know how things work under the hood. If not, even a framework wonʼt help you.