The thing about game engines is that 80%+ of engine developers time is spent on designing tools and a checkbox/slider for you to click. Another 15% is spent on conflits when combining featured. Less than 5% of the time is invested in actual engine features. In raw homegrown engines, you call a function to enable the feature you want. Your 5% time matches commercial engine 5% time. You dont gain much if you know what you are doing. If you dont know what you are doing, well …