A lot has changed in 20 years. The conclusion may still be the same, but spreads are much tighter (thanks in part to HFT) and trade commissions no longer exist.
Trading is hazardous to your wealth, period.
Most of the reported difference in net performance is due to the impact of commissions and spreads: As trading goes up, gross return was not impacted, but net return was.
Retail investors in 2000 were getting fleeced. (And if you think that's bad, take a look at commissions in 1980.)
And judging from the rest of the comments, sounds like there will be lots of short term capital losses also to offset the gains. Also sounds like having lots of taxable gains might be a pretty good scenario here!
In US.