I do not doubt that others can make $ with triangles, trendlines, etc. I just do not know how to do it myself. The problem is that there is no way to know when to start and when to end them. They are subjective.
A moving average, a Bollinger band, an oscillator: these things I can understand. Once you have set some rules for what the parameters will be, these become objective. I am more comfortable with these. Once you choose the parameters for these types of tools, you have essentially chosen the time frame, which is the ingredient that is missing with pennants, flags and such.
I personally am too concrete to trade subjectively. I make rules, and I follow them at all times, including when I feel like an idiot for following them. This can be done if you backtest enough to have faith in your system, and do not overparameterize it.