I don't think random blogs should be ruled out. Just because a blog is random doesn't mean its untrue.

The reputation of the writer matters a lot. Recent models seem to be pretty good at evaluating author credibility as well.

What's dangerous is treating information from an anonymous author as factual. You gotta check that in other ways.

It should not be seen a credible source though.

It can be, but that's hard to correctly judge on at scale.