I think there's a lot of explanatory power here, but I think you undersell the degree to which other fortuitous circumstances happened at the same place and the same time.

Many ancient societies would have benefited a great deal from higher literacy, but the technology wasn't really adequate to support it. Literacy is especially valuable when written material becomes the fastest and cheapest way to transmit information. When one has to laboriously write everything by hand (or carve wooden blocks, or whatnot), even if many people can read one text (but not that many before it's damaged or destroyed), it really limits what can be created.

For instance, Romans were monogamous, and first-cousin marriages while not illegal were generally looked down upon (well before the arrival of Christianity). Romans were also comparatively literate for the time (estimates are around 15%). But although the Romans surpassed the capabilities of later European societies in some aspects of engineering and administrative structure well into the Renaissance, they certainly didn't surpass even pre-Renaissance Europe in making paper (or cloth suitable for printing), which is one key component that enables literacy. (Likewise, the Gutenberg printing press was motivated by and made famous by printing a (highly abridged) Bible, but that was a good seventy years before Luther's Ninety-five Theses.)

Furthermore, I think you stress too much which things are just plain consequences and which things mutually support each other. Literacy supports individualism by making people less dependent on each other for information, but individualism supports literacy because written works allow you to do your own thing. WEIRD is weird in consistent ways in large part because the whole set works well together (at least the EIRD part).

That this had anything to do with oppression is, I agree, completely unsupportable. The traits that work well in a high-technology individualistic society are universal features of the demands of that type of society. Eating isn't a "black" thing just because our African ancestors had to eat earlier in history than any other group (because the others didn't exist yet).