The old men's voices—beneath the columns of false marble (16)
When he mentions the columns of false marble, Pound is singling out England's boring, tacky middle class for criticism. Basically, he's saying that you can't just go and buy some cheap stuff that looks like Greek columns and expect people to think it's impressive. Great art doesn't care about the prices of things. It doesn't even think about money at all. Only beauty counts, and the false marble columns here are a symbol of how the money-obsessed middle classes are just cheap and tacky, like the columns they put in their houses.
Discreeter gilding, and the panelled wood Not present, but suggested, for the leasehold is Touched with an imprecision… about three squares (18-20)
Not only does the middle class tend to decorate poorly, but they do so in houses that don't even belong to them. In this passage, we learn that the house with the false marble columns is actually a leasehold, meaning that the people living in it are renters instead of owners. In a world where people's relationships to things are this temporary and uncommitted, Pound asks us how we can ever expect to pursue worthwhile goals, especially when it comes to beauty.
Propped between chairs and table… (73)
When he imagines the boredom and inertia of the English middle class, Pound tends to focus his criticism on the image of a plain dinner table, where he can picture middle class people sitting and barely holding themselves upright. Since there's nothing worthwhile motivating the people from this class, we can't expect them to contribute much to the history of humanity. Instead, they just play out the same boring dinner-table conversations over and over.
Another day, between walls of a sham Mycenian, 'Toc' sphinxes, sham-Memphis columns (78-79)
In case he didn't make his point earlier, Pound revisits his image of fake or "sham" home decorations trying to capture the glory of ancient Greece (columns) or Egypt (sphinxes). But of course, the whole effort is doomed to look stupid and cheap to anyone who actually knows what they're talking about.
House expulsed by this house, but not extinguished (83)
No matter how much the cheap, boring middle class tries to turn a stately old house into something tacky, it can never quite "extinguish" the dignity that this same house used to have. In this sense, Pound is saying the same thing about culture. The middle class might ruin art for everyone, but it can never totally erase the glory that art once had in the past.
The old room of the tawdry class asserts itself (89)
One last time, Pound tells us that no matter how much beauty tries to shine through in the modern age, the boring, superficial people of the world have a way of beating it back down. And no one does this more than the middle class. For Pound, we should basically have the same classes as in the middle ages: the rich people who support artists, the artists who get supported by the rich people, and the humble craftspeople who practice more practical art on a daily basis. In general, the guy isn't a fan of modern society's whole deal, from its art to its social structures.