On Igros Moshe, the question is whether his position is applicable today. Of course, R Moshe opened this line of questioning by using sociological arguments himself.
Did the life changed enough to re-evaluate? I don’t know in this case, but I already remarked before about a clear case where IM is not used properly: in his argument (for those who are working and according to your reading are already baalei gaava!) that college is not necessary because one can lead normal life without it. That was said when college was an exclusive institution, when now “college” is a basic requirement for respectable employment and often reduces to remedial middle school. This is not a fantasy and not an emanation about R Moshe’s views on eruv as in the other thread, but a simple fact.
It maybe it is worth re-reading published polemic between R Dessler an (anonymous) R Schwab. If I recall correctly, R Dessler acknowledges that Frankfurter approach produces observant people, but not Talmidei Chachomim – and the latter requires Litvishe approach. Interestingly, by now, we have Litvishe yeshivas being recommended for everyone, albeit not in the Frankfurter approach. As relevant to this topic, pre-WW2 writings about exclusive learning are probably directed towards a tiny minority of Jewish community.