I never became comfortable with neither the scope of systemd as a project, nor the ever expanding set of skills required to effectively use it. I was tempted to use the word mastering, but that would make the goal seem even more elusive, especially since with every new version one's knowledge would have to expand to cover its new features. 10 years later, it still looks to me like the project with a solution for everything in the IT industry, following trends, trying to cover all the bases. Always new things to learn, always the goalpost moving further and further.