People that rely on indicators absolutely misunderstand the concept behind the uses of it because it was used to predict the trend which the market may poses but it does not guarantee that the analysis is totally right which is why most senior analysiser will always tell people that their predictions is not trading advice.
Using indicator to predict a long term investment is absolutely impossible but I think it works mostly for day traders and I think if it has not really been working for them, there would have been a lot of discouragement about it.
Indicators are very useful in predicting the real situation of the market, but like you said, most senior analyzers do not rely on technical analysis alone; they mix both technical analysis and Fundamental analysis to conclude at their own prediction. If prediction through indicators for a short term trade is to be looked into, it should be from pro traders because indicators alone will never work for a newbie.