The way out is to focus on the game. Only build up the engine to the point the game needs it to be built. The bulk of your focus should be on game logic, even when you take writing the engine into account.

Granted, I haven't finished my game this way, but the engine isn't really the bottleneck. It's deciding on, and implementing, appropriate behaviors, often for silly, fiddly corner cases.

Exactly this. After lots of trial and error I’ve found it easier to build better engines by extracting and abstracting the common elements from my game development process than focusing solely on engine development. Really can’t describe how much my productivity has gone up since I switched my focus by adding constraints to my development process and narrowing my focus to more parochial problems instead of always pondering the general/wider abstractions. It seems that abstractions are the natural consequence of focusing on a narrow and concrete problem, but people instead try to directly jump to the wider abstract space without any bounds or constraints set, and eventually overwhelming themselves.

Developing the engine is so much more fun though.

I think this is why developing emulators is fun. Once you’re done, the games have already been made for you!