A good course usually goes through 2-3 rounds of revisions before they are good. For some of my courses, I thought after the first revision, the course is ready! After teaching that course to live students, I have discovered gaps and better ways to present the materials and only after tweaking the assignment landscape a few times, the course was finally at a point where I felt it was self sufficient.
You too will not create a perfect course on your first attempt. Creating a course in your head that's never tried to real students in real time are just imaginary courses that most likely won't work in the real world. Only a course that has gone through at least 50-100 students and that have 95%+ success rate (meaning 95%+ of students are able to complete the course with very little outside support), are what I would consider as good courses.
This is similar to what my English teacher at college told me too that first draft/revision is never perfect. For me, I wonder if my third/fourth draft were ever perfect but I can tell my later revisions were definitely better than my first draft.