It seems like Zuckerberg is saying that these "reaction" buttons better address the needs of Facebook users than a "dislike" button because they express "a wider range of emotions." And certainly the "sad" and "angry" reactions can be used just like a "dislike." In summary, "reactions" are what the people wanted, and then some.
A quote from designer Geoff Teehan echoes these sentiments: "Binary ‘like’ and ‘dislike’ doesn’t properly reflect how we react to the vast array of things we encounter in our real lives.”
True, but people will still complain until they get an actual "thumbs down." In the end, you can't please everyone. But now, you can at least "Wow" and "Angry" them.