There is nostalgia involved, for sure, but I question the idea that it's for a supposedly glorious pre-multicultural, multiracial era. The BBC version of the show always had a very mixed bunch of amateur bakers, with a surprising number of men, and the most popular winner by far wore a hijab (and kept it clean while baking!). The real nostalgia, I think, is for the days when people baked at home instead of grabbing something at M&S.