"Whoever wants to be a lover of the world makes himself an enemy of God."
I don't think many of us consciously want to be lovers of the world, more often than not we are seduced. I have heard it said time and again, "It's not a sin to be rich". That may or may not be true. Last I checked greed was still a sin, and wanting more than you need is greed.
If we listen to the voices of the world, we would believe that we have a right to acquire as much as possible as long as we don't break some human law. As if that is the only law.
You ask but you do not receive because you ask wrongly, to spend it on your passions.
And passion is not limited to lust, sometimes it is just the passion to have more.
How many of us can even properly distinguish between need and want? Concepts like the common good and duty to society have all but vanished from our consciousness. Profit is seen by many as the primary good. If the answer to the question, why do we exist, is "to make money" then perhaps if you are a Christian you need to reexamine your purpose.
St. James uses harsh language, but perhaps from time to time we need harsh. We are called to be the stewards of this world and lovers only of God.