> It constantly invalidates its own technology every 2-3 years

I'm not sure about that. Unity itself is not at all a particularly modern engine (just like most engines being iterations of something designed in the 00s or early 10s)

Rule of thumb in AAA: After 3 years devtime you are starting to pay serious debts by tech updates - that’s the descent into development hell.

This. It’s easy to criticize or idolize from the outside. When you’re in it, any time spent beyond innovating is wasted R&D. It might be justified. It probably isn’t. This is one of the main reasons Unreal went open source. Let the community drive R&D on their own dime.