> but it (like ranger) doesn't seem to support this out of the box
No utility can support cd-on-quit out of the box because a spawned process can't send the $PWD to the parent directly when it quits. It needs tweaks in your shell's rc file. nnn also needs the same instrumentation.
Yes, as a user I feel nnn was extremely disruptive as a FM. As the author I see at least 7 to 8 FMs drawing inspiration from it, which is a very positive testimony.
Can you please elaborate what you mean by "half baked"? nnn has macOS users and I believe the number is picking up given we are getting more bug reports from macOS users recently. Knowing macOS users, we can consider polishing some crude corners if the problem statement seems reasonable.