Depends on the purpose of the blog. I maintain a blog for two reasons. One, writing about problems and their solutions as if I'm explaining them to someone else is a great way to solidify the concepts in one's mind (similar to rubber-duck debugging[1]). Two, having an active blog is a signal to potential employers that you're active in the ecosystem. Even if someone is rehashing the same old topics in their posts, seeing how they think and how well they write can be a useful indicator.

[1]http://en.wikipedia.org/wiki/Rubber_duck_debugging

Those are both reasons why it is in your interest to write a blog. They are not reasons why someone might want to actually read your blog (short of prospective employers).

It's interesting that this is the focus.

So all writing of fiction is pointless because everything is just a reworking of previously used tropes?

Unless it's the exact same solution, I think there is always something to be gained.

Fiction is read for the fun of reading a different take on the same basic tropes. Most programming blog posts are not read for even remotely similar reasons.

At the risk of sounding trite, so? Is any of what you just said a problem we should be worried about or a sign of something bad?