It seems to me that the Buddha perhaps considered social reform (SN 4.20):
Then as he was in private retreat this thought came to his mind, “I wonder if it’s possible to rule legitimately, without killing or having someone kill for you; without conquering or having someone conquer for you; without sorrowing or causing sorrow?”
Mara then tries to encourage the Buddha to pursue this:
“The Blessed One, sir, has developed and cultivated the four bases for psychic power, made them a vehicle and a basis, kept them up, consolidated them, and properly implemented them. If he wished, the Blessed One need only determine that the Himalaya, king of mountains, was gold, and it would turn into gold.”
But the Buddha rebukes this, saying that a mountain of gold would not be enough for even one person.
I find the sutta bit hard to interpret, but it might be saying something like “even in a post-scarcity society, governing still means sorrowing and causing sorrow because people always want more”.
However, the way the Buddha organized the monastic orders seem to radically depart from the social hierarchies of the time.
You mention DN 2 in the essay:
“I can, great king. Well then, I’ll ask you about this in return, and you can answer as you like. What do you think, great king? Suppose you had a person who was a bondservant, a worker. They get up before you and go to bed after you, and are obliging, behaving nicely and speaking politely, and gazing up at your face. They’d think: ‘The outcome and result of good deeds is just so incredible, so amazing! For this King Ajātasattu is a human being, and so am I. Yet he amuses himself, supplied and provided with the five kinds of sensual stimulation as if he were a god. Whereas I’m his bondservant, his worker. I get up before him and go to bed after him, and am obliging, behaving nicely and speaking politely, and gazing up at his face. I should do good deeds. Why don’t I shave off my hair and beard, dress in ocher robes, and go forth from the lay life to homelessness?’
After some time, that is what they do. Having gone forth they’d live restrained in body, speech, and mind, living content with nothing more than food and clothes, delighting in seclusion. And suppose your men were to report all this to you. Would you say to them: ‘Bring that person to me! Let them once more be my bondservant, my worker’?”
“No, sir. Rather, I would bow to them, rise in their presence, and offer them a seat. I’d invite them to accept robes, alms-food, lodgings, and medicines and supplies for the sick. And I’d arrange for their lawful guarding and protection.”
Though the sangha clearly wasn’t founded for the purpose of providing social mobility, in practice ordination seems to possibly provide a path out of oppression for the socially disadvantaged.
Here we see kings willing to bow down to their former slaves, and not being willing to re-enslave them.
In the sangha as well, I assume junior monks and nuns of a higher caste would have to bow down to and respect their elders of a lower caste.
It seems to me that ordaining under the Buddha could entail a rise in social status for members of the lower castes that would have been otherwise impossible in the Indian society of the time.
Something to consider I guess.