is it sensible to build a Trading System completely from scratch?

I agree with you that indicators have value in trading.
On the other side I think, that “statistical advantage” is in fact “predicting future” to some extent :slight_smile:

You can also call it “educated guess” or “an edge”, “skill”.
In the end every name comes down to below statement evaluating to true:
AverageProfit * WinRate% > AverageLoss * (1-WinRate%)