The very main reason VR isn't taking off is because it has no killer app, that is, an app that other platforms can't have, and that people love. End-of-story.
What's to understand here is that it's not said that this killer app "exists". If VR is only a cooler screen, then it will sell like cooler screens. Now maybe it's a killer screen, that is a screen that everybody wants. I guess there is a competitive advantage of thinking like that, but right now, vendors think they are making a software/hardware platform when they have no killer app.
This is the kind of 3d engines I was making as a teen. The way it works is that you iterate over x screen-space, get a "ray"/"slice", then you iterate over z camera-space (goes inward) using that ray. From there, you have what it takes to sample a heightmap. Draw a vertical line. There is plenty of room for optimizations and it's very good for learning to code.
Are there any good ideas to improve one's coding / design skills significantly ?
There might be in the CRs you're mentionning. In other words, my advice would be to get the most out of those CRs as you can. Ask questions, encourage people to be critic with you, understand their point of view and learn. If you CR is rejected, get to the core of why it happened technically.
A broader one: writing expressions as much as possible. Basically, it means avoiding unnecessary mutations (and jumps).
Then avoiding architecture. Thinking algorithms that process data (instead of "systems") has been transformative.