Agreed, it's very difficult to make it work.
Also, I would add that it's totally dependent on the demeanor of the wearer, something that often get lost in a clothing focused discussion (perhaps we use the reputation of the poster as an equivalent).
I´m confused. Please tell me why a dark shirt is not a good thing?
Nothing is wrong with a dark shirt by itself, perhaps in the context of a club or something. With a tie and jacket, it murders the contrast you generally need for those elements to look good.
If you are wearing a tie for business reasons, a dark shirt violates business dress norms. If you are wearing a tie for aesthetic reasons, then why pick a background that renders it either invisible or faded? Either way, dark shirt is a no-go.
I'm guessing the same principle applies in explaining why light ties are so much harder to pull off than dark ties.
I suppose you could wear a dark shirt with a light tie and a light jacket and still get the same aesthetic contrast...but it would be an inversion of what is seen as standard and people would probably register it as being very odd.