Earlier quoted context omitted.
Mostly I believe this too, but I am familiar with some people who can consistently make money year after year. From talking to them it becomes clear that they understand things very, very deeply. See /u/Fletch71011 on reddit-- he's always happy to discuss things. He's made millions trading options, mostly algorithmically as I've understood it. The methods he uses are sufficiently complex that you need to be very well…
A 50% chance to lose money per year still allows for very long strings of success. Some strategy's trade ~80% chance of a small win for a ~20% chance of a large loss which means lucky streaks could last for decades.
I agree with you in that it is a possible explanation, but I disagree in that it is the only one possible.