This is actually a good question, and I do think, a lot of "failed pros" try to become coaches or make money creating training material. So as with anything else be a critical consumer. If someone claim to be able to teach you how to beat micro or low stakes, then its probably fairly obvious, why they wont rather spend the rest of their life doing that themselfes for a low hourly earning. And maybe the course is also free or available for a small amount of money.
But if someone claim to be able to teach you how to crush the high stakes scene, and they want you to pay 1.000´s of dollars for their insight, then its a fair question, why they are not out there doing all that crushing themselfes. So at least check their track record, and if most of their proven results were years ago, its probably fair to ask, if they are still as much at the cutting edge, as they claim. I think, there is a lot of stuff out there, where people are asked to pay big money for content, which is often basically some solver outputs.