I may have been one of those who've said not to worry about retro parts, period correct or catalog spec.
For mez retro bikes tend to be about what I wanted but couldn't afford back in the day. That tends to be frames rather than components, though there are of course parts too.
The frame is what a bike is all about, it's how it looks and feels. Components are bolted on and do what they are designed to do, some are better than others, some more reliable, some better looking etc.
Some things are not as functional as more modern bits. Harder to find replacements.
My formula for builds is to find a nice frame, refurb if necessary (I try to buy ones that don't need it, though I've done it a few times), then fit parts I know I like, work and can look after or get spares for.
As I'm a bike snob, this tends to be 9sp xtr (never got on with m900 despite it looking lovely), that tends to be m952, m970 or even m980, or xt equivalents. These tend to work well on most bikes and don't look out of place on an old frame.
V brakes over cantis all day long, even if the frame has a canti stop. I just prefer them, though they have to be something nice.
Forks are just better the newer they are, though retro forks can look amazing compared to newer forks. CNC and carbon character over more generic modern looks. If retro, I try and find a way to upgrade, if modern, something with Vs and as good as I can get (32mm Sid's or fox, pace rc39s).
Wheels, harder to find decent rim brakes these days but crossmax, spinergy or hope hubs and Mavic rims are just fine for me.
Bars, stems and seat posts can be anything, though I'm sad and like things to match. 31.8 bars, no problem, though happy with 25.4 too, whatever works for the build.
Consumables like chains, cassettes and cables, whatever works and looks good with the rest.
I then sit back and admire how good it all looks on the retro frame, as that's what I want to ride.