[potato3732842]

That's exactly my point. Troubleshooting an intermittent problem on a bathroom fan in a subdivided triple decker with common grounds -> hard.

Doing the wiring in a new house (yours or otherwise) -> easy.

The fact that you're making a mountain out of a mole hill her really just screams that you have no experience with ANY of this. The stuff that's hard to "do right" is the stuff that you get one shot at (like concrete) or stuff where the feedback loop is very long (it may take decades to find out that your poor flashing job is letting water in and ruining your siding). The stuff the internet likes to screech about like plumbing and electrical and framing are way easier to validate the quality of because you can test them or because problems will become obvious quickly.

[quesera]

> Troubleshooting an intermittent problem on a bathroom fan in a subdivided triple decker with common grounds -> hard

I would generalize that to "locating and safely fixing problems inside closed walls or ceilings -> sometimes hard".

Sometimes easy still, but that is where things get complicated, and sometimes dangerous. I've found dead-ended intermittent lines left inside walls without any attempt at proper termination, for example. This is how fires start.

Doing your own electrical work exposes you to the lazy errors made by other people in the past. You learn not to be those people (some of whom were licensed electricians).