@Maxperson
Here is what the UA6 playtest Paladin says for 5e 2024.
Charisma, the ability to influence and inspire others is a central mechanic and concept. It also relates to helping a group maintain morale to fight for a cause.
"To stand against corruption" relates to maintaining ones own personal integrity. What one says and what one does, need to match.
"To stand against annihilation" relates to a meaningful, self-sustaining, enduring, Material Plane.
There are many different kinds of Oath, including nontheistic and theistic. The motive for the commitment might be out of idealism or desperation.
The Oath is the magic of words and meaning.
Divine magic is symbolic, linguistic, and relies on meaningfulness. Words create the multiverse. Oaths transform the multiverse in a meaningful coherent way.
A "blessed" warrior connotes the Divine power source from an Astral paradigm, archetype, or ethical ideal. The ideal empowers the transformative effort to cohere the world to the idea. Those Paladins who are Good, strive to make the world a better place.
Paladins are aggressive. They are warriors, and champions, and able to face adversity and adversaries. They are wholehearted and Fight with integrity.
Not all Paladins are Good. Some are Lawful championing a group, some are Chaotic championing individualism.
An Evil Paladin is less an option in the Players Handbook. But the Evil ideal would also be wholehearted and consistent, and transforming its community toward predatory self-empowerment.
Paladins are warriors, but their ideological magic expresses a higher priority.
They are very much the magical champions on behalf of a CAUSE.
Here, "annihilation" literally means to cease to exist. But the implication is, for the Material world to lose its meaning and purpose is the same thing as to cease to exist. It would be the end of the world as one knows it.
Here, the Paladin class description gently suggests how the class might fit within a particular choice of setting.
Here, the description offers a rationale for an adventuring game.
The above is what a "Paladin" is.
The archetype of the Paladin comes from the reallife historical traditions, relating to the knights and chivalry. The reallife inspirations are sometimes deeply Evil. For example, during various crusades, knights were often hatesgroups that committed atrocities against innocent Jewish communities across Europe and into Asia. It is ok to remember that D&D is borrowing from traditions that can be "fanatical" and harmful. But the UA6 Paladin doesnt lean into this darkside.
The core Oaths are: Devotion (compassion), Glory (heroism), Ancients (hope), and Vengeance (justice).
The adherents of these causes can be calm, reasonable, fair, and sane.