The English and US notions of class are very different. In the US, class basically mean income bracket. In England, class is more akin to "caste", a basically hereditary status which correlate with wealth, but it not determined by it. A broke aristocrat is still an aristocrat, a working class person winning the lottery is still working class, even if they stop working. A family may migrate from one class to another, but it takes multiple generation.

The angle of the article seem to be that the English notion of class is bullshit, because it does not directly correlate to wealth and privilege. Maybe so, but class is still a real thing in the sense it affect peoples attitudes and interactions in real way. It is like saying "race" in US is bullshit. But it is still a very real thing that affect peoples lives.