WRONG!!!!
It does take knowledge to be a trader but traders that know what they are doing make more money than buy and hold investors.
Back in 1985 (when I was working for Pru-Bache), I got sent to the Chicago Board of trade. There I met a trader that rented a seat on the floor of the U.S. Bond market and he was seen as a "god" to traders. He started with $25,000 and in 2 years, he had made $200 million dollars "trading" bonds. He would make as many as 50 trades a day.
The idea of traders is simple. Make more money than is lost. Being right or wrong is not important. What is important is to make money profits than losses. He showed me what he did and that has helped me in my trading.
Back in 2010, I traded at stock (don't remember the name) that I bought at 21.50. One year later, the stock was at 28.50, meaning that an investor would have made 30% profit in buying and holding.
I traded the stock 18 times during that year, with shorting the stock 11 times and buying the stock 7 times. I had 13 profitable trades and 5 losing trades and I made 5 times more profit (after losses and commissions were subtracted).
I have met a lot of traders that are consistently successful. I am one of them, even though I am too old to day trade, meaning that I do short-term trades (1-9 weeks as a rule)
Recently (the last 6 months), I have not done much trading on anything. The market has not been clear (too much uncertainty), meaning that trading "and" buy and hold investing has not been easy or clear, which in turn means doing mostly nothing has been the best way to go. I normally trade about 300 times a year. I have traded less than 10 trades in the last 6 months.