there is no proof that TA is a self-fulfilling prophecy. people always say that, but we have no idea how many people are following TA (and remember, everyone's TA is different too). we really have zero clue whether TA could change the outcome of markets.
and these traders can't be independent of the underlying economics---they just add liquidity to existing supply and demand. they might alter supply and demand, but why would we assume they negate it entirely?
this makes markets more speculative and volatile. but i see no reason why TA is "running the market" so to speak. TA is merely a method to analyze the underlying supply and demand. it's completely secondary to the actual economy.
"We are not damaging the market, we are just supplying liquidity".
Turns out that was not the entire truth.
there's a difference between "liquidity" and "extremely leveraged liquidity". market depth is good because it dampens volatility and reduces slippage. but if the source of said market depth is massive leverage, that will enable black swan events that can cause cascading liquidations and extreme volatility.
it's not traders that are the root cause of this, but financialization.