I totally disagree, and I have the exact opposite reaction. Markdown is something tons of people know already. I literally just glanced over the article and felt I could generate a "narrated PowerPoint", which seems like the main purpose of this, extremely quickly. Why would I want to learn a completely new language because there are some trivially minor syntax oddities with using Markdown?
btw, for narrated powerpoint, you can actually use Video Puppet directly with Powerpoint files - just put narration into speaker notes. Here's more info on that: https://videopuppet.com/docs/powerpoint/
Because you already have to learn a bunch of new stuff, since Markdown does not support this use case.
You could easily borrow some common things from Markdown to make things easier, but this seems to try to force following the Markdown syntax as much as possible, even when that syntax makes no sense in context.
It is much better to invent new things for the cases that are completely new, than try to force a square peg into a round hole.
The perfect is the enemy of the good.