Content has to come from somewhere. Operational complexity is increased, not decreased, since you are running a build server in addition to your CMS. The benefit is easier optimizations in the frontend.
Yeah, but you're only running your build server some of the time (which is favorable in this era of by-the-second pricing) and you're running it inside a private network where nobody can try to infiltrate it 24/7 for no good reason.
I actually feel like Gatsby will be developing a CMS to round out their paid feature-set. I have zero-inside knowledge, just a hunch that to get customers to pay up handsomely, the product needs a deeper "fit" in the publishing pipeline.
Content can come from text files. Operational complexity ought to be neutral (or even negative) if that content compilation step replaces your CI pipeline.
