Some people didnt using any indicator , but still profits because they were familier with market habbit and could identify in which level price will bounce or pullback. Personally i am still use indicator to help identy trend continuation or reversal.
Not only. If people don't use indicators, then they use a chart. For example, you can completely do without indicators if you are well oriented and know how to correctly identify levels and trendlines. Be it global or local. The price always moves from level to level, sometimes making deceptive zigzags, but in the end it still comes to the desired level. If you know how to analyze all this, then you will not need indicators.
Also, some argue that if you use graphical analysis and focus on levels, then they need to be reinforced with additional signals based on indicators, because there may be a false breakout of a level or trend on the chart. I cannot agree with this, because in 4 years of trading I have never used indicators. In order not to fall for a false breakout or confirm the correctness of your signal, simply use higher timeframes on the chart.