Writing ability is on the wane in general. In professional settings, IMO this is mostly due to the disappearance of secretaries and clerical staff, lousy education and more non-native speakers.
A long time ago as an intern, I had to re-typeset and format some reports published by a .gov since the 1910s for reprint and web publishing. You would see variations in style, but the reports started getting worse in the early 80s, and are almost incomprehensible today.
It may also be because university education used to be for those with a great interest in science, and I guess for some reasonably intelligent upper class folks with nothing better to do. The first group had the motivation, the second group the habit and education to express themselves well. Today it is for those who want to get a good job. The education for a job majority lowers the standards for everyone.
Btw I'm a middle class guy who did it mostly for job prospects and such, so...
A long time ago as an intern, I had to re-typeset and format some reports published by a .gov since the 1910s for reprint and web publishing. You would see variations in style, but the reports started getting worse in the early 80s, and are almost incomprehensible today.