@Ken, all of the above for those that a) understand b) can use & apply. I don't do TA, nor follow the crowd or use candles. I'm just numbers & pattern type ... savant style trader. GLTA that see the benefit from TA, Algorithms, CNBC etc ... its basically too late.
I use only technical analysis in trading. Do not rely on fundamentals or news. A friend asked me one day, how do you get into stocks that suddenly, rocket up on huge volume? I said, you have to get in before the big move. Otherwise, it is too late. That said, if you miss that move, you will get an opportunity to get into that stock at some point. A failure of any stock pattern, gives you confirmation of the opposite trend. That is a no brainer. You have to be able to control your ego about being wrong and take the opposite trade which is a high probability trade.
Like everything, it works sometimes, in some conditions. TA can work well in markets (or individual tickers) that aren't currently driven by fundamentals/news. But fundamentals and news will always break technical indicators. TA can show you where institutional buys/sells happen (sometimes). It's a tool among many. It's also really difficult to backtest technical indicators manually. Automation/algorithms that can test millions of permutations helps for both backtesting and feature selection. But it's no cure-all.
Ask yourself the simple question: do you focus on the back mirror when driving forward? This is all you need to know to decide the validity of TA. A moving average can tell you where you are and how got here. But it has zero predictive power. Nor do any other price formations of the past. But then those who constantly lose money will grab onto anything that promises help.
The ideas from TA work very well. Momentum, detrending, and relative volatility. But, only smart traders know how to really use this stuff. If you can put these ideas together with some professional level knowledge then you can get a real edge. Examples of professional level knowledge.*** Knowing the treasury market - bonds, bills, and notes. Interest rate futures and spreads. (You should be aware that the largest and most influential markets are interest rates and rate differentials.) You can trade rate differentials by trading the difference of interest rate futures. Knowing how to build custom and synthetic indexes and portfolios to give you aggregate market information for real time comparisons. Can compare (or aggregate) related instruments like SOX, QQQ, and XLK. Another example would be FDAX vs Eurostoxx50 vs Nasdaq or something like large cap vs small cap. (Again, can trade relative performance by trading the difference of instruments.) You can track (and trade) the relative performance (over any timeframe) of sectors and indexes. You can add index and rate futures together to make synthetic portfolios (stocks + bonds). TL/DR If you combine pro trading ideas with TA concepts like I said you will start to become competitive with the traders that are actually placing informed trades. This kind of stuff is what the algo's and machine traders are doing. The reason is that some of these types of trades are less risky than just trading a single instrument's price. The CME has rules in place to help you trade these kinds of things.