All of the sins are 'classically' branded so as to minimize or infringe on their basic meanings which are natural and healthy drives and aspects of simply being. Yes they can be abused - all things can be abused - but they can also be quite harmoniously applied and kept in check by discipline and experience.
Greed equates to ambition, from which an individual both develops themselves and their situation, as well as builds a family from.
Pride equates to self esteem, the satisfaction from accomplishment, and the application of aesthetics (Jordan Peterson: clean your damn room).
Gluttony is the pursuit of nutrition and sustenance, the excessive consumption of which is what keeps people alive during deficit and famine. That 'actual ideal body' pic in /ub/ hints at this.
Lust equates to both sexuality and sensuality, both of which are healthy and necessary aspects of an inter-personal relationship as well as the means to actually conceive children.
Wrath is the righteous expression one applies against threats to house and family. Its the "Momma Bear" drive.
Sloth is the natural recuperative and regenerative drive be it sleeping, resting from exertion or post injury/illness.
Envy is the competitive drive, from which rivalries are born. Having an opponent, challenging them and doing one's best leads to a greater manifestation of the self.
All of the Mane 6 liberally and regularly display these sins with abandon and a lack guilt. In some cases, the display of these are part of their inherent personality and shapes the pony that they are. Where would Rarity be without her pride? Or Rainbow Dash? Twilight (early on) would rather read her books than engage in intimacy (Lust), and now she's the Princess of Friendship. Fluttershy is greedy for the affection and acceptance of animals. Oh, and watch the season 2 finale and tell me there's no wrath.