As to charity shop books, I think a lot of 'better' books get passed from person to person before they ever get donated, especially if they are recent release hardcovers. I know I pass along books to friends and my daughter; and only a few get donated.
Perhaps I'm a bit of a snob. I have on occasion picked up a book to read and can't get 30 pages in without putting it down for being silly, and wondering how on earth it made it to being published. But like others say, at least people are reading for entertainment and that is good.
On bookshelves - we have a political news commentator who is frequently on the news. During covid he has filmed from his office instead of a studio, and he often changes the titles on his bookshelf behind him to give subtle messages or bring issues to the forefront. It is quite entertaining and people have caught on, to the point that it becomes a discussion on twitter, and people will purchase the titles he shows. On the day above, he has "Soap and Water', "Safe at School" (a book on covid protocols for children, and "Murder by Milkshake' which was a cold case mystery that recently had some new evidence in the news. He changes his shelf every time he is on the news.