Google's John Mueller said it doesn't matter either way if you put your blog posts on a subfolder of /blog or just on the root directory of the site, without the /blog.
The best part is that John not only said "sometimes SEOs tell you myths about getting better ranking one way or the other - they're wrong."
He even added this line, "sometimes they tell you not to listen to anyone from Google (sometimes they're right, but not this time)."
He said this on a Reddit post that asks, "is it better to have your blog posts as simple pages or add them as blog posts ? I’ve seen some good websites like backlinko that aren’t including /blog/ in their blogs url slug."
Here is a screenshot of John's reply:
Do you believe John here? :-)
Forum discussion at Reddit.