It's true that many of the so called investment gurus that publish a lot of trading books make most of their money being an author and public speaking, rather than being a successful trader. In my opinion this doesn't have to be a bad thing and just because we buy one book for 20 USD doesn't make us the sucker. It's always helpful to learn more about the author before buying his book, some successful authors worked as traders in their 20s&30s and only turned to writing books later in life. When it comes to financial literature there are three types of books. The first one is about financial history, they teach us how the past worked and what successful traders bought and sold to become rich. This is informative and can help if we see parallels today to the past, but we can't just copy the trades.
Yeah true, you should definitely not be upset about any money you spend on learning as long as you are learning. But making you a sucker is the fact that some people buy some stuff from some people and get the most cliche things ever. I believe that you shouldn't do that. If you want to make sure that you are buying something, then make sure that it's actually a good thing in the end. I know that it's not going to be that simple but as long as it exists and it goes well enough then we are going to do well with it.
I personally hope that people will end up with some sort of profit when the time comes and that means we are going to end up with a good chunk of money with the right time, that's how you could end up improving in the end.