To me it has always has been about learning project. I went from 0 knowledge in Unreal 4 to doing this in 1 year and a half. I had a strong programming background before that though (that I also learned through learning projects).
What is a learning project? It is something you want to do. Do it. Try to. You’ll learn the necessary steps.
Of course the point is not to start off with a MMORPG learning project. But in the case of an MMORPG it could be “I want to do a nice combat system that a MMORPG could use”.
You don’t need to “end” a learning project, lots of them never ends. You just move on to a bigger (or different skill field) learning project.
What is it you want to do with Unreal 4? Well chose a small step and find how to do it. Then move on to another step.