Harris, due to the unusual circumstances behind her nomination, is running both as a largely successful but unpopular incumbent and an agent of change. The respectful but firm questions from Dana Bash were intended to bring out the tension between the two postures. Harris bridged the gap mostly with platitudes and evasions.
It wasn’t very intellectually satisfying, but it was effective. Changing the subject and answering the question you prefer to hear is a trait of all successful politicians. Trump does it all of the time.
The interview didn’t hurt Harris at all, and it was good preparation for the debate. She can expect similar questions from the moderators on September 10.