What a great thread, OP.
There are a few replies here that make me suspect dishonesty dressed as superiority. Unless extraordinarily lacking in self-awareness, I can’t believe anyone genuinely doesn’t care in the slightest what they wear. Your own and other people’s reactions and perceptions are very powerful. How you dress can control an awful lot.
All my life I’ve dressed to fit in. My dad was a tenant farmer and my mum a GP. Too posh for my down-at-heel hometown, not posh enough for my school and university. I dressed appropriately for the people present and the occasion, with a nod to my hosts. A good mannered but uninspiring, even stifling, style. I notice Kate Middleton does the same, perhaps because she’s also caught betwixt and between as I was.
I live in a self-consciously “smart” part of London now, where people are literally well-heeled and well dressed, whether in bespoke tailoring or boho frocks. Nowadays I could afford to dress as they do, but I can’t really, because I’m fat. Yet again, despite having some professional and financial success, I’m still dressed to hide. It’s a capsule wardrobe but it’s basically an adult’s school uniform.
I have an alter ego in my wardrobe full of things I have “collected” for my daughters and nieces. Theatrical, architectural, colourful clothes I would love to wear and never do, and perhaps never will. God I would love to have the confidence to stand out.