Every professional trader said market had changed dramatically over the years, what exactly are the changes? Does the old classic TA trading books still good learning tools? What content can be learn from and what are the parts that new traders should ignore?
For the most part, yes. You still have true believers (including some here) in Donchian Channels, Dow Theory, etc., but make clear rules and do a backtest (or long real-time test) and very few classic techniques will beat buy-and-hold.
The emotions of fear and greed are still there and will still be there for generations on down. Trend following still works and even Richard Dennis had critics who said, trend following no longer works. When some traders put it to a test, they found that trend following still works. Successful hedge funds even now employ trend following. Some approaches do not work because there are flaws that traders ignore because they believe their method is good no matter what market conditions. Some traders rely on news, earnings releases, analysis by hacks on CNBC and Bloomberg and others chase the hot stocks, like the Reddit traders. In short, "too much disinformation and lies". I use stockcharts only to trade, do not pay attention to CNBC and Bloomberg (part of the Sling TV package so, cannot cancel it on its own--however I do not watch it) and actually, cancelled CNBC from my channels so, saved monies in the process too. Any information out there, by the time, you get it, the insiders and hedge funds have already taken their positions at favorable prices. You are just cannon fodder at that point.
So where's some hard evidence of trend-following still working for long market cycles--say the last 30 years?
Nothing beats buy and hold over long periods if it is in a taxable account. Traders will protest, but exceptions don't change the reality.
I disagree. I have been trading for the most part of my life (+ 30 years) and yes something changes, like going from fraction to decimal, or the pdt rules, or the tax code or htf trading, other players, more global 24h markets but for the most part it is still business as usual. A solid foundation of knowing what is important 30 years ago is still the same in today's world.
disagree. Electronic trading, computing power, improved access to financial products, financial Innovations of new products, and the financialization the economy over the last 25 years have changed the markets and the economy forever.