You're right: Writers can get their work shredded in writing groups or workshops, often for the wrong things (it can be a case of the blind leading the blind).

But the trend started way before social media. It began with the rise of creative-writing programs and their tradition of "workshopping" fiction in classes, which can turn into that shredding.

There are still lots of authors writing well from passion and in their own voices. It's just getting harder to find them, alas--in part, because of the death of newspaper and magazine book sections, which used to look for and celebrate those things. Now social media have largely taken over that function.