I applaud that decision. This was a novel about the "regular" people of Paris. Those who you pass on the street every day without notoriety. You never notice what is going on with people, those "average", every day people right in front of you. The placement of the celebrities - almost in a name dropping way, was a plot device used to good end. It gave you a very good sense of what Paris was like in the twenties and the variety of people who crossed paths and never really knew it. It also provided a stark contrast to the central characters and an interesting juxtaposition. Camille has issues with her husband, Pauline has issues with her famous husband leaving her to party with others. Camille appears horrified when Pauline tells her Ernest will come home "roaring drunk". The appearance of Josephine Baker provided the opportunity for a window into Jean-Paul's life, and their "bonding" struck a chord in me. It also provided another view of Paris in the twenties. I really enjoyed how celebrities and the main characters had intersections in common places.
Exactly what Alex George is trying to convey about celebrity I don't know. I can say that for me the depictions showed them as human as everyone else, their failings, odd and difficult relationships, rude behavior, in fact they are relatable and in no way "special" or above the human condition. Jean-Paul says of Josephine " she knew the fragility of happiness , and for this reason, he trusted her." Hemingway also well knew the fragility of happiness - he battled depression for most of his life and eventually committed suicide. Jean-Paul describes Josephine Baker and her celebrity mask and yet... as he says her story has everything.. what more is he looking for ? What more does he want from her? What is it he is expecting? Later he muses that he understands Josephine Baker - France liberated her from the color of her skin.
I think the main point here is that celebrities are just like the rest of us - more recognized of course, but no better, no worse, although certainly while more recognizable not necessarily better known. They possess no greater depth, no greater secrets or stories than the regular person on the street. Some are more complex than others but they are just like the rest of us. Some of us have more secrets, more tragic stories, more successes than others.