Rav Wolfson mentioned in the name of Kadmonim that when Moshiach will come and will usher in the Olam Hatikun, then every aspect of creation that didn't realize its potential (for whatever reason) will finally gain that potential. This includes Reuven, the Bechorim etc...
With that in mind, Shiva Assar B'Tamuz was supposed to be the day that Moshe was going to give the Luchos to Klal Yisroel. If that would have occured in the proper way, then that would have ushered in the days of Moshiach and the Olam Hatikun. Therefore, in "potential", Shiva Assar B'Tamuz in this respect is the most important day of the year.
It is not a coincidence that the Chasam Sofer says that Boaz was Miyabem Rus on Shiva Assar B'Tamuz. This means that Ruach Nishmas Moshiach was then created.
It is also interesting that the Yartzeit of the Ohr Hachaim Hakadosh is "Lavud" (within 3 days) of Shiva Assar B'Tamuz. It is well known that the Baal Shem Tov attempted to meet the the Ohr Hachaim Hakadosh because he had the Nefesh of Moshiach and the Ohr Hachaim Hakadosh had the Ruach of Moshiach. If they would have met, then the Neshama of Moshiach would have been revealed and Moshiach would have come. It turned out that he was never able to meet the Ohr Hachaim Hakadosh because it was not the appropriate time for Moshiach to come.
Rav Wolfson also talked about the Zohar that if one Bais Hakneses (congregation) would do T'shuva, they would bring Moshiach.
I think that we on this forum count as a Bais Hakneses. Maybe with Hashem's help, our Bais Hakneses will be the ones to do T'shuva, and be zocha to bring Moshiach, and enable all the fallen to reach their potential.
Pintela Yid