I'm sorry to hear that. I'll try to explain.
The Quest contains 1.2GB of images. These must be compressed to take up managable space both when running the game and when downloading it. Devices which don't support OpenGL ES3 don't have a common texture format. And the texture formats they do support all have limitations, sometimes serious (like no compressed transparent textures).
It comes down to time and resources. Since release I've spent almost all of my time fixing bugs on different devices. The Quest runs on 3460 different (OpenGL ES3 capable) devices. Most of them work fine, but a few don't. And this with modern hardware and software.
With all those older devices with buggier Android versions and buggier drivers, I'm not sure the result would be satisfactory. We don't really want to release a game which is buggy and slow on a lot of players' devices. Also, it would take a lot of time. We are a very small company, three people. We can't take forever to finish games.
Still, I won't completely rule out the possibilty of supporting OpenGL ES2, but it's unlikely, sorry.
(As for software rendering, the old Quest on iPhone renders a 480x320 pixel image at 20 frames per second, using very small textures using it's software renderer. The Quest on Android can run on devices with 2560x1600 pixel screens at 60 frames per second, using up to 2048x2048 textures. Software rendering it wouldn't even be a slideshow.

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