>use that poop instead of this poop
You have to realize that 3rd party engines require more competence from the developer, not less.
Because you have to know 1. the fundamentals + 2. engine specific abstractions. 
3rd party engines are good for big studios, so they can hire and drag-and-drop random devs without wasting time on teaching them. 
If you start with 3rd party you are just shooting yourself in the foot from the very beginning.