> I wouldn't be surprised if programmers had, collectively, written more game engines than actual games.

Tailored to web developers, there definitively are more half-finished frameworks sitting on people's disks than finished web applications, I'm sure my ratio is pretty close to 1/1 over the years.

I'd much prefer people do this than pump out more poorly-running Unity or UE games.

Oh, that's exactly what I do. My rule is: one game, one engine. It's based on whatever the OS provides of course, or an abstraction layer like SDL, but everything above that is my own, tailored specifically to the game at hand.