I do have formal education in the field, but that doesn’t mean that I’m easily capable of e.g. writing a module for Nginx or even most website frameworks or knowledgable enough about administration to feel comfortable exposing a dynamic website (as opposed to static HTML+CSS) to the internet.
A lot of it is learning by doing, though, and for a lot of things books are a great resource (some stuff is outdated as soon as it’s published, but general system administration or programming knowledge doesn’t get outdated that fast).