Generally, the landing page is not an MVP, it's just that: a landing page. It's a cheap and quick way to get at least some market validation before you start working on your actual product. But depending on the product, It could be little more than a more elaborate form of customer interview (asking someone: would you pay for this? Does this sound like something you would use?), or it could be actually an effective s…
Selling courses work because people buy because of the instructor (hence all this talk about building an audience). They can gauge how good the course is because of the instructor and the product is simple - video access.
However, building complex products or services doesn't work because customers cannot gauge anything about the product or service. The seller is not a good reference point for customers in this case.