So you're answering your question, then? It sounds like you're quite confident that backtesting is important for a trader's success already. I believe nothing can guarantee your success as a trader unless you can see the future.

As far as I know, backtesting is usually used to train or manage trading bots. If you're doing daily trading wouldn't the trading result show whether your strategy works or not? How would you backtest your daily trading strategies? On which app? It would be nice to know if you have a dedicated tool for that.