I believe the term you're looking for is "substantive." A substantive is a word or group of words that are used syntactically as a noun.
In the USA national anthem, the last line goes, "O'er the land of the free and the home of the brave" where 'free' and 'brave' refer to people. Other well known phrases already elaborated on top as contributed by Bib.
Also, the common phrase is "you have to take the good with the bad." I've never heard "you have to take the rough with the smooth"...
The use of substatives isn't a nasty trend, or even a new trend. It's a rather normal part of the English language. I forget if I learned about substantives in middle school English or high school Latin. (Here I removed the word "class" and used just the class subject as a substantive).