The Talmud, when faced with a conundrum that cannot be solved, uses the phrase
יהא מונח עד שיבוא אליהו
Let the issue rest until Eliyahu HaNavi comes (back) and advises us of the Halacha
תשבי יתרץ קושיות ואבעיות
ֵEliyahu (HaTishbi) will answer all the questions.
The question is asked: since Moshe Rabbenu was our greatest teacher, why do we wait for Eliyahu (who never died) to answer the questions, surely we should wait for Moshe (who will be resurrected when Mashiach comes) and ask Moshe Rabbenu to Pasken/decide the Halachic conundrums.
in his celebrated אם הבנים שמחה, explains that to be a Posek, a Halachic decisor, a Rabbi needs to be immersed in the world. A Rosh Yeshivah, for example, who only interacts with the surreal world of his Yeshivah, is not equipped to be a Posek for the masses. All his answers are designed for the שומר נפש, the Yeshivah or Kollel Jew, for whom being יוצא לכל הדעות, acting according to all stringencies, is the norm. Accordingly, since Moshe has not been interacting in our world for thousands of years, he is not suited to be the Posek when the Mashiach comes. Eliyahu HaNovi, however, who did not die, and lives amongst us, so to speak, is more suitable to answer our questions.
It is also for this reason that the משנה ברורה was not considered as acceptable to normative Psak, as the ערוך השלחן. The Chafetz Chaim was considered like the Rosh Yeshivah who lived in his world, and his method of Psak certainly was biased towards accommodating as many opinions as possible. The ערוך השלחן however was also someone who interacted deeply with his community, and for whom the sight of a woman brandishing a chicken to discover whether there was an issue of Kashrus with that chicken, was not unusual. Similarly, although R’ Chaim Soloveitchik ז’ל also known as R’ Chaim Brisker
was considered the genius of his generation in terms of learning and innovation, R’ Chaim wasn’t a Posek. When people came to R’ Chaim to ask a question, he referred them to R’ Simcha Zelig Reiger ז’ל,
the Dayan of Brisk. (Incidentally, R’ Hershel Jaeger once told me that some descendants of R’ Simcha Zelig live in Melbourne).
Rav Teichtal, takes this one step further. He considers it immaterial that earlier Gedolim, such as the Satmar Rav or R’ Elchanan Wasserman had a negative view of an en masse Aliya to Israel. Rav Teichtal claims that they, like Moshe Rabenu, were not there to witness the changes in the world, and so their Psak, for today, is irrelevant.