"The singer-songwriters seem to depend on audience sympathy for the cause -- saving the environment, stopping war, etc -- rather than on well-crafted songs, and their songs are usually tuneless strings of cliche-ridden doggerel"

I agree there's a lot of it about, but they're only a part of a greater whole.Please don't tar all with the same brush! Maybe "some" singer-songwriters or even "most", but surely not all.
As to emotion, it seems to me many younger singers work hard to keep that out of their vocals, probably in opposition to the drivel sung by pop divas at an emotional level equal to being on a scaffold with a rope around the neck, that pours out of supermarket speakers whenever I'm shopping.
The words should convey the emotion, but the singer should be singing the words as if newly discovering them, and without vocal "tricks". If you're honest with the song it will do its magic. However I do think some of the younger performers I've heard, mostly female, sound as though they're singing the songs in their sleep.Almost an academic exercise like they used to be sung when I was in school, without any feel for the content or connection with the story being told.