This book gave me the sense that the author once felt an emotion so deeply that he needed to write an entire novel in order to convey it.
It is a book about many things, but one of the main themes is regret. As a younger person, I thought I would end up following the trajectory of Stevens. The narrative matched mine so much that I thought it was a description of an inexorable path in life that someone like me was bound to follow. As I got older, I realized the opposite: that Stevens was an anti-hero, that I did NOT have to follow the his trajectory, and that I had the agency to make different choices in life. In that way, the book's anti-message guides me today.
p.s. with regards to Ishiguro, despite liking RotD, I didn't care for any of his other works. I didn't like Never Let me Go (which was highly acclaimed), nor the Buried Giant, nor When we were Orphans. Admittedly I have not read "An Artist of the Floating World".
I have read the book multiple times, and that line never fails to move me to tears, even when I know it is coming.