I have thought about just coding a 2D game on Android using just pure Java and the Android SDK, no engines like libdgx, cocoa-2dx attached. I don't know if I really need to use a game engine or not. Doesn't Java already come with basic libraries and APIs for most things already?
I'm not interested in the cross-platform aspect of game engines. The game is 2D, so there's no complex issues with 3D, importers, or what not. I also don't like to have to code around level editors or pre-built constructs like a character or tile class.
Given this, are there any other benefits for me using a game engine to code my Android 2D game? For example, I'm clueless with OpenGL so if I'm doing it w/o an engine I would be using pure Java, would that be significantly slower than using an engine like libgdx?