We found 2 Reddit comments about Keys to Great Writing. Here are the top ones, ranked by their Reddit score.
Keys to Great Writing by Stephen Wilbers.
You hit the nail on the head. I have a friend that has practically given up submitting to agents; her writting is beautiful, but dated. Looking at her goodreads history, I can see why: she loves literature written in the 1800s.
A writing book that seems to echo your exact sentiment is Paula LaRocque's The Book on Writing. Her first chapter is, "Keep Sentences Short, Varied, and to One Main Idea". Stephen Wilber's Keys to Writing also starts the first chapter on Economy. Being concise seems to be an ongoing and important theme in most writing books.