A wise man once said the secret of becoming a good writer is seeking out harsh criticism. This is exactly right. You can’t improve if you don’t know what you’re doing wrong. The best writers tend to also be their own harshest critics; that’s what makes them stay up till 4 in the morning on draft number 15 when other writers are tucked up in bed with draft number 1.
It’s also, possibly, why great writers become less great; they find harsh critics harder to find and maybe harsh criticism harder to take. After all, as in any field, from pop music to politics, once you’ve had some success you’re going to start believing you know what you’re doing. And the prospect of an early night becomes more appealing than an early morning spent tweaking dialogue.
I wouldn’t consider myself a good writer, but whenever I’ve written something that’s gone down well, it’s because it went through a process of harsh criticism; several processes, several harsh critics and several drafts. It’s also why I tend to over-write; because in editing down, you can cut all those bits you weren’t quite sure about. It gives you permission to be brutal somehow. And, eventually, once you’ve cut all the crap, you’re going to end up with something incredibly good. Or something incredibly short. One of the two.
But I wouldn’t seek harsh criticism on the internet. Reviews, I mean. Because it’s too late. Harsh criticism is invaluable during the writing process. Afterwards, it’s pointless. You can't go back and do another draft, you’re never going to write that story again, and next time will be different, it always is.
So if writers don’t engage with internet criticism of their work... that’s why. Because it won’t help them become a better writer.