There's a huge value in understanding Latin, or at least some parts of it - it allows you to derive a vast dictionary of words that have been subsumed into the English language.
Sure there's derivability of terms in English, but the depth to which that is true doesn't really compare.
Most of our Latin-based vocabulary came to English not directly, but via French. So wouldn’t learning French be more useful as a means to building erudite English vocabulary?
Perhaps not, but my rudimentary understanding of Latin - learnt only in passing - has on many occasion allowed me to correctly derive and interpret words I'd never seen or heard before.
However, the rudimentary nature of my understanding has caused me on occasion to derive etymologically invalid words - such as enthnosupremacist - but fuck it, it's English - why can't I mix my etymologies?
(although in this case, I'd probably hyphenate it).
And to an extent far more versatile than anything on the English side of my understanding of language.
Sure there's derivability of terms in English, but the depth to which that is true doesn't really compare.