I did extract from Wikipedia a few sentences that summarize best what TA is - to me:
"In finance, technical analysis is a security analysis methodology for forecasting the direction of prices through the study of past market data, primarily price and volume.
Technical analysis stands in contrast to the fundamental analysis approach to security and stock analysis. Technical analysis analyzes price, volume and other market information, whereas fundamental analysis looks at the facts of the company, market, currency or commodity.
A key principle of technical analysis is that a market's price reflects all relevant information, so their analysis looks at the history of a security's trading pattern rather than external drivers such as economic, fundamental and news events. Therefore, price action tends to repeat itself due to investors collectively tending toward patterned behavior.
There are many techniques in technical analysis. Adherents of different techniques (for example, candlestick charting, Dow Theory, and Elliott wave theory) may ignore the other approaches, yet many traders combine elements from more than one technique. Some technical analysts use subjective judgment to decide which pattern(s) a particular instrument reflects at a given time and what the interpretation of that pattern should be. Others employ a strictly mechanical or systematic approach to pattern identification and interpretation."
Anyone claiming TA "doesn't work" actually claims there are no statistically repeating price/volume patterns which can be traded for a long-term profit.
So, on the anti-TA front, we find people who claim there exist only repeatable situations involving factors outside of market-generated data, leading to trading opportunities with no repeated footprints in the market-generated data ... in essence, repeated input situations generating random price-action but with the ability for those anti-TA people to figure how to actually trade each of these situations (with a random price-action outcome) for a profit ... who's delusional, really?