I think that, as far as 'what Gd wants from us', we have all we need from the prophets. We have the whole story of the world, from its creation through Messianic times, foretold in broad strokes, (why broad strokes). We also have all of the laws and traditions of our people that make up Jewish life, from the Pentateuch, and to a lesser degree from the other books of our biblical canon, as well as the measures we need to take to bring about Messianic times.
Bava Batra 12a, (original text):
Amemar said: A wise man is even superior to a prophet, as it says, "And a prophet has a heart of wisdom", (Psalms 90:12). Who is compared with whom? Is not the smaller compared with the greater?
So prophets strive to be wise-hearted, like Sages! I heard a great interpretation of this talmudic saying from a student at Ner Israel high school, in the name of a Rabbi of his there. Prophets need to be told what God wants. Sages, having studied and analyzed and researched our texts and body of law extensively, already know what God wants.
So, to answer your question directly, We already do know what Gd wants, as prophets have told us all we need to know, so we don't need any more prophecy to tell us. At this point, new prophecy's only real function would possibly be to verify Messianic times, (though we already have plenty of prophecy to verify in that area, maybe we'll need some thing explicit), or to give us instructions going forward into Messianic times.