“I’ve noticed that most of the classic works, especially those translated from Latin, display a use of language, writing and argument, far superior to that of today.”
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You don’t even have to go back that far.
Much more recent examples of richness in expression and a thorough development of ideas, off the top of my head, would be Dickens’ magnificent David Copperfield-written as a mere popular novel for a very general audience, and the simple exchange of letters betwen John and Abigail Addams.
No, you don’t have to go back that far but it’s interesting that all you mention would have been well schooled in the classics and in Latin. We gave up an important linguistic and intellectual asset when we abandoned the classics.
Read some old newspapers from World War II. Longer paragraphs and a greater vocabulary were common, even in the unsophisticated Midwest.
Watch some of the movies of the 1930's. The actors spoke in longer sentences with complex sentence structure and a vocabulary rich with words we do not even hear today.
Part of this is due to the increased use of computers, which feed our "instant gratification" portion of the brain. I noticed last year that I was having difficulty reading long passages, and I believe it is because I am on the computer so much. I also noticed I hadn't been reading books much. I decided that I needed to bring back the long attention span I used to have, and have been reading books in the evenings.
Textbooks are also reinforcing the shorter attention span by catering to it. Just as Sesame Street created generations of children who wanted lessons that lasted no more than 2 minutes (complete with cartoons or puppets), the textbooks are now filled with pictures, cartoons and jolly bullet points to get the attention of children who have been raised on video games, computers, and TV.
Here is my scariest comment. I will bet that my post is one of the longest posts on this forum (in the replies). I have been here since 1998. Ten years ago it was quite common to see longer posts. (An example of this would be the late, great Common Tator.) I have been struck by how few posts are of any length now. And I will bet a lot of you had trouble reading this whole post, because it looked like too many words.