"Learn once and apply everywhere" is a golden key that claims to open all locks. This leads to retrofitting other people's solutions that's inappropriate in your situation.
For example, all kinds of tasks are forced into a todo-list format, even if there are better ways to go about them. What's important is never written, and what's already known is "written for reinforcement." That's because todo-lists seem to be a universal solution to the productivity problem.
A general solution is like an equation with a plethora of variables. It still needs someone to observe and fill them in. So a general solution is not "the solution," but a "solution generator." For example, learning to code is not the same as having written all programs, but the ability build anything as one chooses.
Yet, we are deceived continually to search for and embrace that one marketing plan that beats all, that one course that teaches everything, and the one product that does everything, or that one piece of skill that makes you able in all things.
The whole purpose of a general solution is to be able to generate specific solutions rapidly, and not to replace the need for specific solutions.