Technical Analysis can be broadly divided into two categories,
“Trend and momentum following indicators”
“Predicting with repeated patterns (Elliot Wave )”
The 1st one has a huge inventory of indicators. The technical analysis by Elliot wave, also has WITHIN itself innumerable possibilities. Both methods are being used by a large number of people with moderate to poor results.
The reason for success rate not being universal has very interesting reasons which I will try to enumerate below.

Let us take the case of technical indicators 1st. As markets do not behave SIMILARLY at all times, both trend and momentum indicators can fail at times. (Markets can be overbought and oversold for long period of time ) However being overbought OR oversold CAN give a warning to be cautious.

The problem is not with the indicators but with how they are put to use by a individual trader. The correct use cannot be learned in a single day ALTHOUGH one can learn about these indicators in a few hours. By correct use I mean the correct application learned through years of experience where the markets teach you whenever you go wrong. Of course the learning period can be shortened by getting a mentor who has learned through MARKET EXPERIENCE, the correct way of application of indicators to the market.

The above anomaly is even more pronounced with using elliot wave. It can take years of practice to correctly decipher what the chart is saying, when using elliot wave theory. Patterns become more and more familiar as one goes along. It is just not enough to understand the basic theory of 5 waves up and 3 waves down. It is only by years of practice and pattern recognition that one gets a FEEL when markets are turning around. Market by itself is a great teacher and will humble you as you go along. Like technical indicators , Elliot wave too requires mentoring to get the true practical knowledge for correct usage of the wave theory.