When my daughter was in middle school, she said, “You know the problem with public transportation? There’s too much public on it.” She got over that, though. It’s a really narcissistic attitude.
I use public transportation in Philadelphia regularly (although I normally commute in a car). I haven’t seen feces ever, even when I was using it every day 30 years ago. There are definitely a few yucky spots in the awful underground warrens under Center City where you walk to transfer between lines there, but the trains/buses and stations themselves are fine. I also use it in New York, Chicago, and Washington (where, of course, it is immaculate).