FWIW (I'm the author) my creative output was ~0 while I was working a 'normal' job. I worked really hard and didn't have much energy for tech stuff outside of work (especially since I wanted to live a life that included non-tech things!)
I think it's totally fine to not make stuff outside of work, and it's so impressive to me that some of my friends manage to make creative stuff in their free time while working a day job.