Something too long for a comment, and perhaps deserving of more than the potentially-ephemeral state of "comments":
First, specifically, in the late 1960s and through the 1970s, at least, for mathematics, a hugely significant fraction of important papers and textbooks were not in English. They were in French or German, and many things were in Russian, but the American Math Society translated some of them, with a year-or-two time lag.
When I was in grad school, it was absolutely essential to be able to read mathematical German and French (and Russian would have been good, but this was never available in high schools, and rarely in colleges/universities, but/and was luckily supplemented by AMS's translations).
That is, in those decades, there was no "Latin" for mathematics, at least.
But that was not a serious issue!
But, yes, then and now, less-devoted scholars, and "outsiders", will not have earlier anticipated the "need" to learn suitable languages... so, yes, certainly, coercing publications into a single vernacular language will make things more accessible.
That is, to recap, although multi-lingual science was never a serious obstacle for substantive professionals, it obviously could have been, and be so still, for people needing information that does not require comprehension of languages beyond their native one.