The important corollary here is that not all language needs to be poetical. It's OK to use generic language in a lot of situations. Sometimes "I'm very sorry to hear that ____" is the tool for the social situation.
I believe that the original meaning is lost [or warped at least] when it becomes synonymous with bleak, cheerless, chill, Cimmerian, cloudy, cold, depressing...
But since it means ‘slow’ it also relates to blue, dejected, depressed, despondent, down, droopy, hangdog, inconsolable, low, melancholic[0].
Compare "I was sad to hear about your grandmother" or "I was very sad..." with "I was morose..." or "I was inconsolable..." When it really matters, you need to drop the pretensions from your writing and just be normal.