Firstly, no Cessna EVER came new out of the factory with wiring like that. I would suggest if your 1957 C-172 had wiring worse than that then it had avionics upgrades/maintenance along the way performed by incompetent avionics technicians.
Really? No kidding. It got that way over 50+ years of additions and subtractions. No arguments about the technicians. Point is, it always worked, never had a problem and didn't present any dangerous situations in over half a century.
Secondly, bundling wire runs into looms is NOT about looking "pretty". It's all about organisation and safety. Bundling wires gives them superior support, limits unwanted movement, takes stresses off connections, and greatly reduces the possibility of wires chaffing on the airframe.
Organization, I will buy...safety, well, that is a subjective thing in this discussion. As has been posted, there are many, many examples of this kind of wiring that have stood the test of time with no adverse effects to the user. The rest of the statement I have no argument with; all of the examples you list are great examples but history has shown that the rat's nest has not necessarily been dangerous.
To me, dangerous building is about poor workmanship leading to a significantly increased possibility of an adverse outcome. I think that's pretty much what I see in the photo posted by the OP.