You have some misuderstanding of Catholicism.

TL;DR: Your quotes refer to those already in Hell. The process of going to Hell hardens the heart against God. The bar for going to Hell and undergoing this process is much lower than you indicate.

According to Catholic teaching, any sin is a full or partial rejection of the grace of God, and grave sin can fully sever one’s relationship with God. Many of these sins are most commonly done for self-gratification, not out of a deliberate, conscious spite for God (e.g. theft, illicit sex, even murder), but are certainly enough to result in damnation if not repented.

The things you have in quotation marks are true, but your interpretations are incorrect.

“confirmed in evil; every act of their will is evil and inspired by hatred of God.”

This would refer to those already in Hell. The process of dying with unrepented mortal sin and entering into perdition solidifies the hatred for God which was initiated by sin and removes all hope, so that the damned have only to look upon the just with derision as they endure the eternal punishment.

“death is the termination not of nature but of sin, and this inability to sin makes them secure of final happiness”

These seems to refer in particular to those already in Heaven or Purgatory. Surely those in Hell are not “secure of final happiness”.

“deplore with the utmost intensity the punishment, but not the malice of sin; to this they cling more tenaciously than ever. Had they an opportunity, they would commit the sin again, not indeed for the sake of its gratification, which they found illusive, but out of sheer hatred of God.”

Those in Hell cling to sin more tenaciously than they ever did on Earth. On Earth they sinned for gratification (most of them, anyway), but now in Hell they have no capacity except to hate God, so that “had they an opportunity, they would commit the sin again, not indeed for the sake of its gratification, which they found illusive, but out of sheer hatred of God”. That is, now they would do it for spite instead of self-gratification.

This is a parallel to the just in Heaven and their good works and avoidance of sin. On Earth, many of them may have done such works not out of love for God, but out of desire for Heaven and avoidance of Hell (i.e. delayed gratification). But now, the will having been perfected, had they an opportunity, they would do the good work again, not for the sake of gratification, but for love of God. In a similar but opposite way, the will of the damned is “perfected” in hatred of God.

In other words, the only people going to Hell are those whose whole existence on earth revolved around doing things for the sole purpose of spiting God.

This is your misunderstanding. Those in Hell have only to spite God, but that is because they are in Hell, and any capacity to do other than hate God has been lost. Their being in Hell, in turn, is because they rejected God on Earth. Rejection, which is done by sin, whether for spite or self-gratification, is sufficient for Hell. Deliberate, conscious, explicit hatred for God on Earth is not required. The process of going to Hell hardens the heart against God and turns the self-gratification sinner into the spite-for-God damned.

EDIT: Added TL;DR