Well, that is the "commotitized the complements" part.
The other part of your argument is that it is/was good enough for most users.
But let me put the question this way: If had it been 3x more expensive than the Mac, would have it been successful?
If not, then there's a clear distinction between a great product and a great price.
Remember the 3 Ps (Price, Product, Promotion)? Product and price are different things, specially in the software market, where the price doesn't necessarily reflect the cost.
So if people would not buy a 3x more expensive Windows, great product it not the motive by which it was successful.
I think the most accurate explanation in this case is not that Windows was a great product, but as another commenter said, that it offered a better value proposition for the money invested - and Microsoft had not the better product value, but the better price proposition, so they won that equation:
MacOS had a product value of 10, and a price of 5, so the value proposition was 2.
Windows had a product value of 5, but a price of 1, so the value proposition was 5, for each dollar invested.