Your comments are a very good starter. So is it fair to say that for recent scholars such as Kühner-Stegmann-Gildersleeve & Lodge-Allen & Greenough, Latin is chiefly learned and studied as "pure science" because its value as a medium of everyday communication let alone for new literary creations has dwindled so much as to be almost non-existent; whereas for Renaissance scholars, Latin was only "half" as dead then, so they still learned and acquired Latin as a living thing, for self-expressions, etc. etc.. They were sort of like modern day bilingual or trilingual, ready to switch between (medieval) Latin and their respective vernaculars. So while the differences in between are well known to them, there is perhaps really no need nor space for them to overthink or overanalyze any part of either languages (or dialects)?
The other question is, which you may or may not have read prior, did any of the ancients who were really proficient bilinguals of Greek & Latin, Greek and Sanskrit, etc., etc. firmly believe or hint these were "sister" languages back then? Or is this language family thing a modern concept/invention only? If the affinity between Greek and Sanskrit were so obvious to a scholar like Sir William Jones, were the ancient themselves totally oblivious to this? If they had been so blind for so long, perhaps that's another evidence that people from different eras do have very different perspectives when it comes to relationship of languages.
https://en.wikipedia.org/wiki/William_J ... ilologist)
Jones is known today for making and propagating the observation about relationships between the Indo-European languages.
PS
Didn't see any mention of the contribution from ancient sources in the development of the concept of "language family" as we know today in the Wiki entry below:
https://en.wikipedia.org/wiki/Language_family