Yeah, building on what Nick said: I think it was possible at one time, 7-8 years ago, to launch a course on Udemy with no audience, and let them handle the marketing for you.
I heard a podcast recently and a successful Udemy instructor had said that these days, the SEO required to succeed on Udemy is even harder than the SEO to rank in Google. When you search for a topic on Udemy (eg. React, Go), there are dozens of highly-reviewed courses, and it's impossible to show up in those results unless you already have a huge audience or want to spend lots of money on paid traffic.
So yeah, I think it's true that you need an audience to succeed with a self-published course, but honestly I think that's true no matter which route you take.
For big categories, less than 5% of total sales comes from search traffic so if they're primary concern is ranking in search they've already missed the point.
The vast majority of sales are from their personalized recommendation widgets and email blasts. No SEO optimization needed for that.
I heard a podcast recently and a successful Udemy instructor had said that these days, the SEO required to succeed on Udemy is even harder than the SEO to rank in Google. When you search for a topic on Udemy (eg. React, Go), there are dozens of highly-reviewed courses, and it's impossible to show up in those results unless you already have a huge audience or want to spend lots of money on paid traffic.
So yeah, I think it's true that you need an audience to succeed with a self-published course, but honestly I think that's true no matter which route you take.