When I was young (20s) I always flew Y on long haul international routes (mostly TPAC from Japan). Back in those days (1990s and early 2000s) all the TPAC flights were 747s (10 abreast) or early build 777s with 9 abreast seating. Y seats were tolerable for a long flight. Nowadays I am fortunate to fly either J or premium economy on all my lomg hauls, but I've seen Y in 10 abreast 777s and 9 abreast 787s, and the seats look horrifically small. The only times I've flown Y in those configurations have been on short domestic flights in Japan, where most passengers are thin. There was one time I flew with my son (then 9 years old) and put him in the middle seat. The stranger next to him was average size by Western standards and was spilling into my son's seat.

These days I avoid Y and just pay for PE or J on every flight.