Right. To her credit Foot saw the error and reversed her position:
And isn’t [the justice/rationality problem] the fence at which I myself have repeatedly fallen, trying now this way now that of getting over—from ‘Moral Beliefs’ in 1958 to ‘Morality as a System of Hypodietical Imperatives’ in 1972?[7] All of this is true, and if I am hopeful of greater success this time round it is because I think I now see why I couldn’t have managed it before. Roughly speaking it was because I still held a more or less Humean theory of reasons for action, taking it for granted that reasons had to be based on an agent’s desires.
[…]
I have therefore, rightly, been accused by my critics of reintroducing subjectivity at the level of rationality while insisting on objectivity in the criteria of moral right and wrong.
Philippa Foot, Does Moral Subjectivism Rest on a Mistake?, 4
That last sentence along with her admission that, “Morality as a System of Hypothetical Imperatives,” can never do what it pretends to do is very obvious to those who are not restricted by the modern paradigm. For example, take the idea that Foot was going to get to properly ethical truths from the foundation she set in MSHI. Hypothetical imperatives are obviously not going to generate “disinterested justice,” no matter how they are arranged. It always seemed a hopeless paper to me, and I’m glad Foot saw that in the end.
The key for Foot was to escape the modern Humean paradigm—that “Humean theory of reasons for action”—and this went hand in hand with a return to Aristotle.