I have been told that there have been no further prophets since the last of the Hebrew Bible was written ~2500 years ago. Without prophets, how do you know God's will? Who is a valid messenger of God -- whom do you trust?
I ask this question out of curiosity and do not intend to be disrespectful.
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.
the Vilna Gaon in his commentary to Mishley (Parables) 16:4 asks your question:
וכשהיו נביאים היו הולכין אצל הנביאים לדרוש את ה' והיה הנביא אומר ע"פ משפט הנבואה דרכו אשר ילך בה לפי שורש נשמתו ולפי טבעת גופו וזהו לאדם מערכי לב שלו לא היה רק לערוך לבבו לדרוש את ה' בכל לבבו ומה' הי' מענה לשון ע"י הנביא איך יתנהג וכשבטלה הנבואה היה רוח הקודש ישראל ואיש רוחו הוא יודיענו איך להתנהג ורוה"ק יש לכל אדם ואדם אך אשרי אדם אדם לא יחשוב ה' לו עון ואין ברוחו רמיה
And when there were prophets, they would go the the prophets to seek G-d and the prophet would answer, according to the rules of prophecy, the way in which [a person] should go according to the source of his soul and according to the nature of his body. This is a person's preparations of the heart" [this a reference to Mishlei (Parables) 16:1] - he only had to arrange his heart to seek G-d with all his heart, and "the answer of the tongue is from G-d" [the continuation of Parables 16:1] - through the prophet - how he should act.
And when prophecy ended there was the Jewish holy spirit and each person his spirit will inform him how to go. And a holy spirit is with every individual person. However, fortunate is the man whom G-d does not count his sin and there is no trickery in his spirit. [This is basically interpreting the next three verses there, hence the location of the commentary].
the last message of the prophets was Malachi 3:22-24
"Remember the torah of Moses, My servant-the laws and ordinances which I commanded him in Horeb (Sinai) for all Israel;Lo, I will send you Elijah the prophet before the coming of the great and awesome day of the Lord..."
the Malbim commentary there explains that since there will not be any more prophecy until the end of days, God is giving us this final, general message to keep in mind and guide us until then. see there.
We need to understand the meaning of G-d wanting something from us, because He is complete, he lacks nothing and doesn't want it either. Shlemuth. On the other hand, He wants from us is a figure of speech that the call of reality calls upon us to adapt to changes around us (homeostasis). We are implanted with a desire to improve our condition every time there is a change that challenges our state of mind, etc.
G-d wanting from us is the divine call of living a such stable life, to live proactively, in harmony with the natural laws of His creation via the path of Torah. He doesn't need anything from us, but does participate with us and in us in reference to Tiqun Olam. We are his instruments, we are made batzalmo kidmutho. He expresses some his thoughts and will via nature which witnesses everything we do.
G-d is not limited to change by things "me'or'im" circumstances. Since He is stable and independent of creation, we have the obligation to strive to a life of stability, via Torah, (emotional, physical, spiritual, intellectual). We must harmonize and balance our mind, body, and spirit, to emulate the Creator in this world. Things constantly are changing, cycles of events, coming and going.
That is a very tough question to answer, yet extremely important and practical. The prophets of the Tanach have given us major assignments that are still definently applicable now days.
We however lack a Sanhedrin whom will guide us as a nation and prioritize the assignments our prophets have given us. There are many sincere/honest people in the orthodox world whose priorities frequently tend to contradict each other drastically. Eg. To be Zionist or not, to work and learn or recieve tzedakah and learn all day., to focus on pilpul or not, chasidim vs Lithuanian approach, kiruv or not, the list goes on and on and on. Many times these choices lead to complete opposite life goals.
All agree that the outcome is to serve God. I personally am not in favor of the answer that "God just wants you to pick a rebbe, and follow and trust his decisions in everyway" I think that's an easy way out of the self-responsibility Hashem has given each and every one of us.
I personally am of the opinion that god wants you to follow his laws, to serve him wholeheartedly, and to seek the truth, but you must make many decisions on your own. You must choose a path within the confinements of the halachic tradition, that are in harmony with YOUR intellectual honesty and soul. Only then can you find a rebbe to help guide you in your PERSONAL growth and mission.
