Earlier quoted context omitted.
If you want high quality blog posts, you need to know which ones are popular and bring in new readers. Without that, you'll loose a really strong signal for self improvement, and your blog might become write-only...
I don't see anything in what you said that explains the assumption that a popular post is a high-quality post. Certainly if you're looking to build an audience, then the popularity of your posts is an important metric that will help you craft additional popular posts. But it seems to me that the the only _quality_ indicator isn't a metric at all - it's actual feedback from people who have read what you've written.
You can delve into metrics like the time spent on a page but in the long run popularity is the king since it also reflects dwell time.