Like everything these days, it depends. I live in Seoul, where the density is arguably too high. If you get on the line 2 train, which encircles Gangnam and the business and tourist districts, you're gonna be a sardine. If you hop on line 3 far enough east, it's totally chill during rush hour in August. Literally. Air conditioning. Wifi and cell signal. It's luxurious compared to LA.

I think it's just a matter of city planning. In Seoul's case, I think they didn't properly account for population growth and how much the inner-circle areas would boom. Outside of line 2 and some key transfer stations, public transit here absolutely is relaxing. I brag to my friends in the states about it all the time