The great sage isn’t merely required to understand problems and to be creative in solving them. The great sage also has to marshal a huge amount of data. To make a convincing halakhic ruling, for example, no Biblical verse, no Talmudic saying, no medieval responsa, and no modern-day opinion can be overlooked. The Talmud was written in such a way that any one page of it assumes that you already know what’s written on all of the other pages. It feels as if there’s no way in. It’s a formidable work. Jewish law constitutes an enormous web of literature that stretches over centuries and refers at each point to every other corner of the web. It simply isn’t possible to make a legal ruling without intimate knowledge of the entire history of the subject.
So yes, Talmudic scholarship (at least certain brands of it) do necessitate vast knowledge. But lets not exaggerate. As anyone who studied Talmud seriously knows, you are not starting from scratch. The commentators often give you the relevant sources, and cross links themselves. Today the job is even easier with computers. Even when facing brand new questions - odds are that after you solve the first question of how to approach it, your sources are fairly easy to find. Additionally a large part of the "Data Marshelling" is really only a result of the casuistic manner of the Talmud, and the lack of a good editor. The Data Marshelling element of Talmudic study is only a minor part of the story.
Let's have a quick look at another comment Dr lebens wrote:
The founding leaders of Modern-Orthodoxy, whose work really will be studied for centuries, Rabbis Kook and Soloveitchik (and even my Rosh Yeshiva, Rabbi Lichtenstein) were educated in the ultra-Orthodox world before moving toward modernity. We have to admit that the Ultra-Orthodox Yeshiva system, despite all of its faults, has something going for it. As a Modern-Orthodox Jew, I think that our exposure to secular sources and to the modern world make us more intellectually creative and socially sensitive than many of our ultra-Orthodox counterparts, and yet, where is that Modern-Orthodox produced giant that I’ve been looking for?hmm. Is Dr Lebens not aware that the MO movement did not yet have the institutions to create giants when Rabbi Kook (and we will ignore the question of whether Rav Kook can be classified as MO) and Soloveitchik were young? Additionally I'm not quite sure what his definition of a "Torah Giant" is? Perhaps some of todays Roshei Yeshivah can be considered Giants? Perhaps some of Rav Kook's students?
To be fair to Dr levens you should read the final paragraph of his essay, where I finally realized that he wasn't arguing for a total Haredi exemption from the IDF. Sadly, I'm not really sure what he was arguing, or what his point was (beyond Talmud is good, Talmud is hard). Levens chairs the Association for the Philosophy of Judaism - which I was hoping would find a slightly better argument for why we should excuse people from the IDF for the study of the Talmud, then "It is really tough".