If we cannot backtest it and find out if it is reliable or not, a lot of us are just objectively believing it works. Any prove for Elliott Wave work? Personally I have learn how it works and tries to apply it everyday. It "looks" like it works sometimes, but after years of experience, it seem like it is more about my objectively thinks it is a raise/drop trend instead of a real subjective analysis. We have to "choose" if the current trend possible pattern, then the upper time frame bigger wave pattern, and even think about the smaller time frame wave pattern, and all of these are subjective choices in our mind every time when we try to do a Elliott Wave analysis. Then we just see what we want to see, and then we invest by what we feel like and believe.
If it was possible to backtest it would give perfect results as it is always clear when the move is completed. However before completion a good Elliot analyst will always have at least a 2nd option and if two Elliot traders give opinions there will usually be at least 3 options. There are elements of construction that are useful to any trader like an ABC wave, thereafter if might develop into 4 & 5. I've met a few profitable Elliot traders and a zillion that can't make it work so there is a lot of subjectivity as you have found. That doesn't lend itself to backtesting. I learned it from a Jew who made his fortune using Elliot and I'm pretty good at it, but I don't use it as I have better techniques. Advanced Get will always look great after the move but as it progresses it will change the count and that is the problem. When I train traders I spend one session on Elliot so they can identify a clear wave pattern when it is in your face. Apart from that it is too iffy for students as it requires a great deal of experience to develop a good "feel" for it. I'd rather have something that 10 people would all agree on exactly where the entry and reverse or exit is. There is an Elliot Wave thread on ET - why not hang out there for a time and see if you can improve your skills?
There are 3 points that I get from words: 1) You are saying some people in the world using Elliot wave theories to gain profit but you provide no information to provide this Elliot wave theory work at all. Can that be lucky, or they just try to promote themselves so other can believe them and let them earn money through invest for other/ marketing effect? 2) As you said there can be 3 or even more ways at almost any moment that the trend can become, isn't that so subjective even just to decide what is the analysis to come up with these 3 possible outcome? 3 bigger possible changes in upper waves with each of 3 possible lower wave would be 9 possible outcomes already. 3) Since there is no prove Elliot Wave theory work or doesn't work, it could be the biggest extremely well design marketing "weapons" to let people like Prechter to earn so much money just to talk about it for decades and unlimited people buy his books and subscription just because wave theory is such a amazing fantastic "story". As I just said, wave theory may works or just a marketing thing for people who created it or used it to "analysis" to earn from what people need to buy to see what they talk about. We take our own risks to believe in what can be just a marketing thing for decades without we can prove it even actually has any real predictive power.