>There are very few games where the engine is what made all the difference.

Maybe if you ignore the entirety of the retro gaming scene where people are using old engines and modified old engines because they bring along a lot of the feel and expected behavior.

The average modern Unreal and Unity game feels like shit, but some dev's can pull off making new engines behave like old ones we love. It requires a lot of work. Just look at New Bloods catalog of games that pulled it off. DUSK (unity), Amid Evil (UE4), Ultrakill (Unity). Each one of those games had a lot of passion behind them driving for gameplay perfection in the style of a retro game and/or engine.