They've got expensive doctors To cure their hearts of stone. (18-19)
It turns out that our typical methods of fixing problems – like hiring a doctor or a shrink – won't solve this sort of isolation. The heart doctors don't actually address this kind of heart – the metaphorical heart, which deals with all of our caring and loving.
The race of man is suffering (30)
Don't worry. You're not alone. Everyone feels alone. And that's the weird paradox of this poem: everyone is isolated. We're all isolated together.