Imagine we tracked a group of 1000 randomly picked individuals who wanted to be a brain surgeon. I don't know for sure but I wouldn't be surprised if of 1000 randomly chosen people, only 3 people managed to succeed at it after 4 years.
But no one would ever say "Study shows it's impossible for an individual to become a brain surgeon." or imply that it's just random luck to be a brain surgeon. Instead we conclude that being a brain surgeon must be very hard and require a great deal of dedication and commitment.
The reason day trading is singled out whereas brain surgeons are not is that the barrier to entry to become a day trader is very low, anyone can try to become a day trader and many people think they can succeed at it.
The proper conclusion to take from this is isn't that the stock market is pure luck or just a form of gambling... it's that one shouldn't be deceived by the low barrier to entry into thinking that they can succeed at it. It's really hard, soul crushing work to be a successful day trader in much the same way it's really hard work to do anything in life that pays well.