Skilling is not intended to cover everything needed in a course. Skilling focuses on content design and delivery, exercises and feedback, and student monitoring. Other software might be used for other things.
For example, suppose you teach a statistics course, year after year. You might create a Skilling website. Students use the Skilling website to read content, do exercises, and get feedback. Every semester, your students use the same site.
However, for discussion forums, grades, and the syllabus, you might use your university's LMS, perhaps Moodle. Each course section over time has its own Moodle course page, with discussions for that section, grades for that section, etc.