Well, let’s think about it and think about when Our Lord talked about eternal damnation.
Our Lord said we cannot serve two masters, God and Mammon.
He said if our eye was our undoing, we ought to pluck it out.
He described the Last Judgment in terms of separating those who saw the needs of others and reached out as to the Lord and those who saw those needs and ignored them.
St. Paul describes it this way:
For those who live according to the flesh are concerned with the things of the flesh, but those who live according to the spirit with the things of the spirit. The concern of the flesh is death, but the concern of the spirit is life and peace. For the concern of the flesh is hostility toward God; it does not submit to the law of God, nor can it; and those who are in the flesh cannot please God. But you are not in the flesh; on the contrary, you are in the spirit, if only the Spirit of God dwells in you. Whoever does not have the Spirit of Christ does not belong to him. But if Christ is in you, although the body is dead because of sin, the spirit is alive because of righteousness. If the Spirit of the one who raised Jesus from the dead dwells in you, the one who raised Christ from the dead will give life to your mortal bodies also, through his Spirit that dwells in you. Consequently, brothers, we are not debtors to the flesh, to live according to the flesh. For if you live according to the flesh, you will die, but if by the spirit you put to death the deeds of the body, you will live. (Rom. 8:5-13)
When Our Lady warned about sins of the flesh, then, it was not a narrow sort of sin, but rather in the broad sense of the World, the Flesh, and the Devil. By the numbers, yes, I would believe that the sins of the flesh are deadly to
the most poor souls. She did not say these were the worst sins. She said these sins ensnared the most people. It could be the the World and the Devil are the “one percenters” of sins. She never said those were nothing to worry about. She said the flesh was the area that was the grave problem
the most often. You don’t have to be rich or powerful to fall to the sins of the flesh. The sins of the flesh are there to tempt pretty much everybody.
Therefore, Our Lady’s warning should not be taken to mean that we ought to be most concerned about just avoiding a narrow range of sin. That would be a great mistake, and a mistake that the tempter would of course try to ensnare us with: that is, the mistake of believing that the deadly sin most attractive to us isn’t that bad or that we have to be on guard chiefly in one area. No, you don’t guard just one door or one window from thieves. You may watch the ground floor windows more carefully than the second story windows, but that doesn’t mean that all of the windows couldn’t offer a means of entry to a thief.