"walk not as other Gentiles walk" +
Being past feeling leads to lust and greed: Irony here. Desensitisation due to sin leads to more desire, more seeking for pleasure in a disorderly way. Why? Because sin promises so much, but so frequently disappoints. The thing that seemed to be the key to happiness soon becomes a disappointment, tends toward tedium. So people lose their potential for enjoyment of innocent pleasures by seeking them to excess or in illegitimate and selfish ways. Then they try to compensate for this by yet more of the same! E.g., insatiable lust for food, money. And they may even become so hardened and perverse that they can only take pleasure in what is vicious. E.g., sadists and con-men.
The irony of holy living is that self-discipline and moderation lead to greater happiness, partly because the good things of this world thus retain their pleasurableness. But even more because, by these lesser goods remaining in their rightful, secondary place, we are able to enjoy the primary, higher, spiritual goods. We can know God and his many graces.
So, what can we learn from St Paul's teaching about fallen humanity? Because we have been given a new humanity in Christ, as today's Epistle also teaches, we can be soft and receptive towards God in our hearts. In so doing, we will know wisdom.