Someone suggested adding a comparison to the backtest results, showing the profit and loss from buying and holding the asset versus the profit and loss from the user-defined strategy. I think this is really interesting to see.

Unfortunately, I don't have data on the performance of professional traders, so I can't say whether most of them beat index funds. If you have any sources, I would love to see them.

Clearly their tools are not good enough. /s

Prices are made by humans, including the edge case of automation where instructions are still human.

On average not beating an average where there are transaction and membership fees is therefore expected, it could not be any other way. That doesn't however make the index the best predictor of itself.