Their business model is to draw in investors who are willing to pay extremely high fees in exchange for the hope of beating the market. In practice, hedge funds underperform the market, so their investors are paying fees for nothing. The only winners are the hedge fund managers. Enriching people for providing negative value to their customers isn't socially useful.
Along similar lines, the crowning achievement of the synthetic asset quants was the creation of a mountain of toxic three-card-monte mortgage debt that exploded in 2008, bringing down the global financial system, crashing the world economy, impoverishing hundreds of millions of people, and creating the political environment that lead to both Trump and Brexit. Blowing up the world certainly isn't socially useful.
I don't see any downside to reducing the FIRE sector's share of GDP back to what it was in 1960. The economy worked for the median person then; it doesn't work for the median person now, and the amount of wealth the FIRE sector sucks out of the economy to pay for these kinds of games has a great deal to do with that.