I think this is a good balance.
Another way to look at it is from a "theory of change"  mindset. I discovered this idea a few weeks ago, from a HN comment, I believe. You envision some type of change that you want to bring about in the world, and then you work backwards in concrete steps in order to figure out how to make it happen. What's cool about this is that it gives you a clear purpose for going outside of your comfort zone and learning new skills. E.g. maybe you're a programmer, and you want to get the US on renewable energy. You're good at programming, but through your analysis you realize that persuading people (politics) is the most likely path to your goal. So you start improving your interpersonal skills.
As far as growth mindset, it's strange that the article said "Beyond that, there's not a clear way to develop a growth mindset about interests." The canonical book on the topic  offers many more ideas on how to cultivate growth mindset.