Legit question: Is this because of the engine it's running on? My assumption is that if the game had its own engine, optimisation *can be* tighter but the work is greatly increased? I did an interactive digital media diploma using unity, and I suspect it has overhead that causes blanket limitations.

I only ask because I'm using godot now for a small hobby project and it's so easy to use, but I'm not sure how much is a trade-off by using the engine - how "light" is the engine used? 1% overhead? 10% sort of thing? Is this line of questioning even along the right path?