You can categorize game development into 3 stages
1. You have no real game, you are writing physics, camera, rendering and audio code
2. You have a game that works somewhat, you can walk and look around, but everything is still basic and buggy, performance is not good.
3. You have a basically finished game, it executes some complex stuff that is specific to your game. It has no major bugs and performs well. 

The problem with unity, and off-the-shelf engines overall, is that they allow you to go from stage 1 to stage 2 easily, in 20 minutes basically, but the tradeoff is that they make stage 2 to stage 3 transitions much much harder. Unironically it's immediate gratification versus working on your fundamentals. 

>>390138912
Game development is very hard, and the payment is very bad, with the amount of skill required to make a good game you can easily score a job at FANG and just extract normalfag money while doing very little. And making a good game in unity is even harder.
 
And making good games in VR is unironically might be at least twice as hard.
Look at the pic related for example, is a frame from elden ring, it's a custom engine but it is good to illustrate the point.
If you don't understand what you are seeing, I will explain. The elden ring engine starts GPU work only after completing the CPU work completely, (well, GPU doesn't idle completely during that time, because work from previous frame overlaps, it is still extremely inefficient and high latency). They still shipped the game and sold millions copies, but that kind of stuff just not going to fly in VR.