Technical indicators work because they work.

Really - it works because other traders decided there are price points of significance based on mathematical equations and act on it. Traditional technical analysis could be seen as looking for a set of technical indicators that optimally describe the amalgamation of TA and the capital it controls on the market at the moment.

But nowadays it's very hard to make it work.

Ofcourse they don't work. If they did work why would anybody tell you about them?. The fact that they use thier time to tell you about them rather than trading and making money means that they do not work.

If technical analysis worked, the conundrum is that revealing the secret would result in the world following the chart, which would have the effect of changing the indicator so it no longer worked.

Presumably anyone who ever found a technical indicator that worked would: 1. Currently be wealthier than Elon Musk; and 2. Never tell anyone the secret.