I have noticed that it is easiest to create game with JavaFX. Also it is not difficult to find tutorials.

LibGDX is more complex, but the advantage over FX I find:
Better or faster way to set up basic games tasks. Ability to use 3D graphics and its effects: shadows, physics...

I have seen several games on Youtube made with libgdx, they are just platformers.
Platformer also could be made no problems with FX. I dont see really advantage into learning this.

Im unsure about Jmonkey/ LWJGL. They both contains complex code, that I cannot comprehend:
Java Code:
while ( !glfwWindowShouldClose(window) ) {
			glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // clear the framebuffer

			glfwSwapBuffers(window); // swap the color buffers

			// Poll for window events. The key callback above will only be
			// invoked during this call.
Jmonkey atleats have more friendly PDF books. Perhaps Im wrong, but it seems that LWJGL just focus on graphic. And if I do not demand my game to have HD, I see no reason to spend time on learning these.
Or im wrong?