I think he's referring to the horrifically unmaintained and archaic state of the world's older subways, like NYC and the London Underground. Besides the expense, NYC is absurdly behind on modern train timing systems, which causes very loose scheduling and frequent delays. There's also the general squalor and lack of maintenance of the platforms. London's tunnels are so full of iron dust and other particulates that a half hour in them literally turns your mucus black, and the lack of a cooling system has caused the ambient temperature to rise ~30 degrees since their construction with no sign of stopping. They also screech loudly enough to cause permanent hearing damage.

These systems could be modern and effective, but instead they're disintegrating in place. That's the problem.