Unless you’ve written one before, it’s the natural learning curve.
You can always generate one using LLM if you don’t care about how it actually works.
> You can always generate one using LLM if you don’t care about how it actually works.
Lol, right. That might work for some of the runtime parts of a very simple engine, but not the other 90%, especially when you "don't care about how it actually works".
A game engine (like UE or Unity) easily exceeds the complexity of an entire desktop operating system (not necessarily in line count, but in number of features, their diversity and complexity).
And if you have written one before, it might take five years. ;)
At least, that was my actual experience at a game studio. The engine team wanted to rewrite the engine but underestimated how much was there, how much was worth keeping, and how much work needed to be done. But that was a long time ago, and the studio’s now on Unreal.