This is an excellent point. At that point you'd need so much abstraction that you'd basically be building something as complex as the underlying engines.

In rare cases that works out, like for Caves of Qud, but mostly because of the nature of the game: https://news.ycombinator.com/item?id=37548720

The best most folks can dream of is decoupling some of their game logic or mechanisms from the engine somewhat, like what Captain of Industry did:https://news.ycombinator.com/item?id=31588018

That said, I'm surprised that engines like Stride or NeoAxis don't try to imitate the Unity API more - making porting from another engine easier, or being able to reuse some of your existing skills would surely be a good selling point!