I don't think there are any failures in it - it could have grown outwards to become what React is today, or something, but it always kept to the principle of do

I don't think there are any failures in it - it could have grown outwards to become what React is today, or something, but it always kept to the principle of doing one thing and doing it well: unifying browser APIs across vendors and simplifying them. (yes, I realise that's two things, but...) These days there are many fewer differences between vendors, and things like the Fetch API are making the kind of simplifications jQuery pioneered a core part of the browser experience.