The people telling me that longwings (or open laced shoes in general), medium or light gray suits (and I saw flannel suits included for a WTF moment) aren't CBD appropriate astound me. Rewind to the 50's for a moment. What was the iconic standard attire of the conservative city businessman? Mid gray flannel suit, black longwings, often in a pebble grain or shell. Made by Florsheim, of course.
What was once the beau ideal of conservative attire somehow, through iGent reinterpretation, becomes inappropriate for conservative settings.
This is kind of getting the wrong lesson IMHO. While there is a long-lasting conversation in menswear that is important, since connotations of different garments today are often dependent on the functions of their ancestors, going through arcana of the 30's or 50's and trying to replicate exactly is the wrong way to figure out how to dress today.
Sure, you can wear a mid-grey flannel suit with black longwings in shell. You will look like a businessman. From the 50s. There's nothing wrong with that, if you like the look. But the idea that it's perfectly normal and unremarkable dress in, say, modern day DC political circles or NY banking circles (I'm guessing - less direct experience here), is ridiculous. It's not "wrong". But at the same time, it's not what everybody else is wearing. People are a little more familiar with it at this particular moment because of Mad Men, but that's not necessarily a good thing, as now you're the Don Draper wannabe.
This is not (or at least not exclusively) an iGent interpretation. It's a modern interpretation. There's a reason all the politicians wear dark suits and white shirts. Just like all the businessmen and news anchors you see on TV (sportscasters are a whole nother cesspool). It's the modern day business uniform. It's what you wear today in formal business settings in many industries when you want people to think that you're serious but don't want them to talk about what you're wearing. Which is usually what you want in a formal business setting.
As Fok said, for many meetings in California, this would be ridiculous. You show up in suit and tie and everyone else is in hoodies. This is almost as wrong, unless you're comfortable with your dress being conspicuous.
If you want to go for historical accuracy instead, just show up in morning dress and have done with it. Don't forget to bring a wallet full of photos of business being done in morning dress in the old days to show everyone else how correct you are and how wrong they are.