If we already understanding about price action will be not necesary to use indicator because from the historycal price we can decide which support and resistance area. I have seen many professional trader just use 1 indicator only for trading, the more important thing is knowledge about how to read price pattern.
For the short term, maybe the indicator is not really needed because you only need a candle on the chart. but for the long term
certainly indicators are very important to determine when you have to buy and sell