I never really went too far down the rabbit hole of these things. I use them to post PDFs and little else. Can you get so locked into these CMSs that it's hard to teach a course without them?
I'd say it depends on the course - I use a few short recordings to teach basic techniques, and then provide worksheets for the seminars based on those. I could teach the course without this, but I'd end up with less content and more time doing basic troubleshooting rather than exploring more complex examples.
Overall, I've found a good VLE takes some work to set up once, but pays dividends in work saved later - I don't need to remember to upload a list of tasks, or answer emails of "I missed the lecture because I saw a flying pig, what are we doing..." because it's all up there without me needing to do much except tweak release dates at the start of the year (one afternoon's work).
The trouble is when you move to a new platform and... Well, hence my post!