This is true, but also the game in question was coded entirely from scratch, which is part of the problem: the majority of those 3 years were probably spent dup

This is true, but also the game in question was coded entirely from scratch, which is part of the problem: the majority of those 3 years were probably spent duplicating the work done already by Unity and Unreal. If you want to make a living as a carpenter, you don't start by planting walnuts.