You'd get the same cross-linguistic benefit by learning a modern Romance language, and/or by learning the meanings behind all the Latin roots in English (depending on what kind of benefit you're talking about).

The period when Latin teaching was mandatory was a time when education was limited to the elite, and before the purpose of education was seen as to be 'useful' in the way we now see it. Rather the study of Latin was in order to induct young men into the foundations of Western civilisation, and thereby to socialise them into the elite. At this time (18th century and before) to be educated was to know Latin and Greek.

And in fact, the sorts of modern schools that also existed at this time (and which continue to have kind of a similar ethos) haven't stopped teaching Latin, e.g. see the elite New England schools such as Deerfield Academy and Phillips Exeter Academy (where Mark Zuckerberg studied it).

Though it's true Latin is no longer such a central part of the curriculum as it would have been in the past, as even among social elites, learning practical subjects is much more important than it was when to be educated meant knowing Latin and Greek. It's only today that the study of learning Latin is advocated primarily in terms of its utility, this isn't how it was thought of in the past.