I ran an ISA company for a while and can say with pretty high confidence that there are many reasons why fee-for-success is not an effective way to monetize this type of content (Which I've written about before [0]).

I agree that a business, like YC, that has been around for a while, monetizes directly with a fee-for-success model, and has good reviews is very likely to be effective. But the inverse does not hold: a program using fee-for-service is not particularly good evidence that the program is ineffective.

[0] https://twitter.com/seanlinehan/status/1505923007096700939