@Quincythequince
I think your ideas on interview attire are very rigid and quite dated - and certainly wouldn't apply to every role or sector.
I'm a manager with recruiting responsibilities. I work for a very, very long-established, formal professional body, in a role where I have daily contact with the CEO and various board members (think of the kind of place where most of the board members' titles are Sir, Dame, Professor, Lord, Baroness etc).
When I interview people for roles in my team, all I care about in terms of their appearance is that they are clean, tidy and dressed in a way that would be acceptable in our offices. If someone's hurt their foot, of course I don't care if they wear sandals! I don't care if I see someone's toes. It's not like they're getting their minge out. A clean, smart t-shirt with a skirt or smart trousers? Fine by me. Bare arms? Of course. I would much rather someone wore short sleeves on a warm day than sat there boiling hot. Men in my office rarely wear ties, smart trainers are fine, open-toed shoes aren't a problem, etc. I regularly wear dresses with Doc Marten boots, Converse trainers etc. Therefore I don't expect people to arrive for an interview dressed like they're appearing in a 1980s Gold Blend advert or defending a client in court. Fine if they really want to, I wouldn't hold it against them, but they would look out of place.
I'm sure there are places where your kind of interview dress code might be vitally important, but you are talking as if it's a universal truth, and it just isn't.