You don't have to know everything about Digital Marketing as it's such a huge field with so many branches. I do agree that you should just focus on 1 scope first and at least have basic knowledge on the other scopes of DM - by basic I mean what their function is, how they can help you achieve your goals etc. but you don't have to know in depth on how they work operationally. If you're not enjoying the scope you're focusing on, it's okay. Move on to something new and see if it's the right fit for you. When you've somewhat figured that you really enjoy what you're doing, then you can really start specializing in that. You'll eventually know what you like to do and don't, as well as what you're good at and what you're not.