I would disagree with the circumstances being unchanged when applying the words of the tshuva (as far as pusuing professional avenues in order to “get rich”. These days, with all the costs of being frum, even “getting comfortable” is a stretch for most).
But at the crux, R’ Moshe is condemning making investments in ones’ career. He says that those who invest time, money, and effort into developing professional skills is not a ben torah. But is an apprenticed tailor or cobbler any more of a ben torah? One is no less invested in the career, it is only a distinction of delayed vs instant gratification. Rather, he is distinguishing between professional Rebbeim and other professionals- and he is allowing for professional Rebbeim to still be considered bnei torah.
If that is the case, then being a ben torah is not meant to be a universal goal for all frum men. A ben torah must be a reserved term, perhaps the modern equivalent of “chaver” from the gemara?