This is at face value a simple question that most blog writers will find themselves asking more than a few times a day, what is more important to them: the traffic that they get on a regular basis or the content that they write for people? This is not talking about making money, but more of the content or traffic.
In many ways, content is needed before you will get a lot of traffic but at the same time, not getting traffic to a blog can mean that the content is not valuable and this, for a writer can mean that you either are not producing something which to most is a valuable piece of writing or an informative piece or you will not get the traffic that you need to continue your online writing journey.
You could of course learn how to communicate to your fellow readers, but if the content turned them off before, chances are they will not come back to read more. So, content is important to keep readers coming back. This is not about comments but about people visiting your sites and reading them, and potentially adding links to their sites to give you more traffic.
So what about traffic, there are two ways to look at it, traffic for your content that gives you many page views, or traffic which makes you money. So, in a sense, traffic is a must. Traffic will build upon itself, but again without great content, traffic means nothing for your writing career.
So, the more important thing is the content on your blog, then you get the traffic you need to make money that you want.