I don't see how avionics' complexity is relevant. Game engines are complex too. Avionics cannot be developed iteratively, for domain-specific reasons. The cost

I don't see how avionics' complexity is relevant. Game engines are complex too. Avionics cannot be developed iteratively, for domain-specific reasons. The costs of re-testing, re-certifying, and deploying, would be crushing. Besides that, how can an aircraft be delivered if its avionics are unfinished? What's the gap between 'viable' and 'finished' here? Games are of course a different domain.