First, let me say relying just on TA with BTC is risky but I do use it a lot.
TA for sure works. That is not really the question, the question is how often and how accurately. Looking at my (past) record, I'd say it works more times than not and a lot better than guessing. That has been proven over many many years.
If anyone thinks TA doesn't work I'd say you have to try it for a few months after learning it pretty well (spending a couple hundred hours studying and practicing).
To define how it works, that is a tough one. The underlying things we see in a chart are composed of many variables (e.g. emotion, economics, fundamentals (yes!), etc.)
So, I use TA but with BTC I am a lot more careful with it as a lot of BTC is driven on sentiment (aka The world situation). We could be going down fairly hard and if another country pulls a Cyprus - BOOM UP. And vice versa in a sense. But I think all of us know that, the thing is, the world is a tough place today. Some currencies/economies are getting closer and closer to collapse by all accounts and to me, that will be the real determiner - after all it is in large part why BTC is where it is.
Unless you get consistant results above the 50% marker, TA has no added value in BTC and a coin toss suffises.
if you only get 30% and don't consider it the process to get above the 50% marker no value is added.
you hit the nail on the head that BTC is mostly emotion driven. It is not backed by anything then (fragile) trust.
If you have ALL the parameters you can use TA effectively. Marketcap is small and whales are big, reducing your chances of success.
Just keep that in mind.