He seemed to specify no tuxes. A suit and tie would still be less formal than a tux. He also expected a lot of people to not wear suits, but I don't know if that is to mean it is a casual wedding, or that he just assumes it's a casual wedding. A little more info might be helpful.
I don't like your outfit at all, by the sounds of it. Tan isn't formal enough, and neither is a window pane jacket. Wear a suit. In linen, if possible. Wear a tie, but if most people aren't wearing one, you can take it off.
It's also totally suitable for his work life, and he does know how to dress himself. He doesn't need to change. And Yohji is so far away from his current aesthetic you might as well ask him to become a different person.But what do they do for a living? Does how they dress matter where they work? If it doesn't, they can pretty much dress however they like. That's not true of most people, at least not for people who are trying to fit in in their workplace. And so what if the...
I take it you buy $90 t-shirts? How are you comparing buying a plain white t-shirt to buying a car or house? Apples and oranges. Is the quality of the t-shirt so great it justifies the price? Is the difference between that t-shirt and a white t-shirt from Uniqlo so great? It's probably barely noticeable. That's not the case when it comes to cars and homes.
Paying $90 for a plain white t-shirt is fucking stupid. I know some people will try bring up the "quality", but the difference between that shirt and any other white shirt you'd buy at the mall is probably negligible. Well, except for the price.