People also need to realize that what is “close enough” 40 years ago, or even 20 years ago means something very different than today. Hangars have much lower tolerances than they used to for proper functioning. Two reasons:
1- Increases number of gears. Every time a gear gets added to the cassette, it either gets wider or the cog spacing gets narrower. Both of these things exacerbate issues if the alignment is off.
2- And since pretty much everything these days is indexed, you can’t compensate for these issues as you shift.