Rabbi Solovetchik was not against the teaching of biblical criticism at YU. It was tought there to college aged people without the heter Joseph referred to. (By the way I never spent a day in YU, im a Beis Medrash Gavoah alumnus).
Maybe hundreds of years ago there was a need to have a specific reason to not study outside literature. For example they lived much more sheltered lives, so it makes sense that Rabbonim would outlaw it, to keep their enclosed lifestyle. But in todays modern and open world there may not be anything wrong with it.
Or at least one of the previous generations Gedolei Hadar R’ Yosef Dov Solovetchik’s Das Torah was that it isn’t assur. You can’t argue with Das Torah.
(Joseph’s next comment: There IS something wrong with it.)