One of the problems with many traders is that they want a trading system that is highly accurate and that is very difficult to achieve, it seems traders cannot simply accept that they are going to be wrong on their predictions and worry more about that than about their stated goal of making money from the markets.
It is not just traders that want an accurate system but also the investors where they could make money out of it. It’s impossible to have a 100% Accuracy, and no one will ever achieve it just because of the unpredictability of the market.
This is where backtesting enters the stage, since it can allow you to test your strategy against hundreds of markets at different points in history and see how your strategy will perform, if it performs positively then it should be expected that it performs positively over the long term as well if you implemented it, but as you may guess the only way to backtest your strategy in such a way will be to be able to get the necessary data and create some code to do it for you, otherwise the backtest will be incomplete and full of biases.
Even if you backed tested a couple of times or even 1 million times, it’s not a guarantee that you could get that same success rate due to previous times. Something could occur almost the same way, but it’s not 100% the same. Pine scripts are being made for those kinds of testing, but it’s still not perfect.