What's the problem with OpenGL ES 2

[Nemesis2k]

Finally I enabled the OpenGL backend on my Galaxy S4 I9502, which uses the Imagination Power SGX, which only
supports OGL ES 2. The result is better than I expected --- the emulator does not crash and I can hear the sound;
only that the screen is black

From one thread, I know that the Dolphin requires ES 3. But it seems that there is no fundamental reason that
Dolphin cannon run on ES 2, as there is the thread about Dolphin on SHIELD, which uses Tegra 4 with ES 2.

My guess is that the OpenGL backend is heavily based on the desktop OpenGL, whose functionality is not well
supported by OpenGL ES 2, but much better supported on ES 3. So the quick porting can only happen on ES 3.
And with more time and porting effort on the OpenGL backend, it's possible to run it on ES 2 as well.
Is my understanding correct?

What's the development priority for Android Dolphin? If we expect ES 3 device to be commonly used soon, maybe
ARM JIT optimization is the priority; otherwise, maybe porting to ES 2 is the priority as most people won't have
ES 3 device.

[ExtremeDude2]

afaik it can't be ported to GLES 2, that is the whole reason it hasn't been done XD

[neobrain]

I'm fairly sure it could be ported to GLES 2 if someone seriously wanted to. It's just a question how much compatibility can be reached with plain GLES 2. Also, given that the number of people working on the OpenGL backend is extremely small and interest in GLES 2 among those few is basically zero, this is unlikely to happen. And even if someone else came along and ported Dolphin to GLES 2, I doubt the code would be clean enough to get merged into the Dolphin tree.