Cyberpunk 2077

That's only if your employee retention and training are good enough, and you don't plan on growing your team. When adding more developers you either have to invest incredible amounts of time and money to get everyone to that level (and we're talking years per developer), or you'll be left without the ability to really alter it while still having to educate every new developer on your engine.

This approach simply doesn't scale or work out in the long run.