I might have some insight into this one because in the early 00's (pre-blogs), while working in tech, I invested in my social life by writing newspaper columns on men's fashion and style, and have since made it a point to be as helpful as I could to new immigrants to the country to help decode some of the nuances of the culture so they didn't feel like they had to take shit from anyone.
The question I spent a lot of time on in my early 20's was whether mere taste could be sufficient or necessary for class mobility, and whether it could matter by creating real opportunity. The answer is complicated. Jenny Holzer's truism, "money creates taste" is even only partially true.
That book from 1983 is part of a storied genre with a long history of selling manuals to hopeful people, and they're really variations on etiquette manuals and Cinderella, Pygmalion.
First, there is a smarter way to look at it. One of my favourite maxims is from management and political theorist Jeffery Pfeffer who stated, "They forgive you when you win." It's in one of his most popular books, which if you are keeping track, was on one of his Stanford courses, and was on a Davos reading list from the FT. Fancy, surely, but if you start with the insider/outsider worldview, nothing will cure you of feeling like an outsider. One of the most famous gold medalist olympic show jumpers said he only ever beats his last round and the course, not his competitors. That's how you succeed. I'm crassly name dropping these ostensibly fancy things because the other thing someone interested in this stuff needs to understand is that there is no there there. There is no peak experience of luxury that will make you become something, but experiencing it can change you if you understand it, especially with very young people. I think the most valuable experience a child can have is, even for a brief period, to experience real freedom and power, because that high water mark (peak) experience will form a key co-ordinate in their identity, and this can change their life course to a significant degree by just knowing what it feels like and wanting to feel that way again. (just as people often use low water mark experiences to define themselves by their peak negative experiences. btw, if you did this without knowing it, you aren't what happened to you, you are free.)
So, what is that royal jelly, or that magical quality that very rich people seem to have, where clothes just seem to fit, skin seems healthy, and always seeming to say and do the right thing? What is that power? First, it's your perception. Second, it is an effect of other things. English has this almost sinister conflation of effect and affect, which pollutes the downstream culture and keeps people spinning wheels. Third, those things are when you prevail in your endeavours and do that often enough that it becomes a habit, and you just relate the world differently, and that is the effect you sense. Faking it until you make it presumes there is something to make. There isn't. Start with something real and humble and just grow.
Anyway, it would be really long personal exposition on what "class" looks like in 2021, but I'd say yes, it's still a thing, and no, it's not what we think it is, and warn that reasoning about it at all is a trap that subconsciously self-identifies you with a sense of inferiority that is not real, and finally, it's the effect of things you can choose.
Scott, if you are reading this, thank you for writing. You help a lot of people.