Not so sure. After my father died I came across a box of old letters that were sent between he and his friends, from their early college years. Just personal, casual correspondence, which today would be done with a messaging app or email. Even on the short notes, the structure, spelling, grammar, and even the penmanship is excellent compared to what I see people of the same age doing today.

Nope. I have a bunch of family letters, and my great-grandmother put more effort into writing simple "Happy <holiday-name>!" postcards than some people do for their college applications. And she worked on a farm, and only had just 5 years of formal education.

The modern devolution of spelling is just not giving a fuck about norms and courtesy.