Not even the encouraging words of a private equity titan could brighten the mood of some of the world’s top hedge fund managers.

“Don’t be embarrassed about making money,” David Rubenstein, the billionaire co-founder of Carlyle Group, told attendees at the SkyBridge Alternatives Conference in Las Vegas on Wednesday. “It’s been a great industry for the U.S. and created a lot of jobs and made companies valuable. You shouldn’t be upset about that.”

Rubenstein had kicked off the annual gathering of hedge fund managers, encouraging them to do a better job at defending what they do. Yet just hours later, the masters of the universe -- criticized for making too much money for themselves by some, and for making too little for investors by others -- were again on the defensive after a large investor in the funds spotlighted their lackluster performance.

In the past two weeks, the $2.9 trillion hedge fund industry has been criticized by billionaire money managers Steven A. Cohen, Warren Buffett and Daniel Loeb over talent, fees and performance. Cohen said he was “blown away by the lack of talent,” Buffett described the industry’s fee structure as “unbelievable” while Loeb said funds were in the early stages of a “washout” and their performance this year was “catastrophic.”

For Leon Cooperman, the founder of Omega Advisors, it was time to reminisce. The period between 2000 and 2007 was a moment in the sun for hedge funds, a “golden age” as he called it. These days, managers who want to compete will have to cut fees or look to complex computer models for help, he said, a trend he’s not inclined to embrace.

"At age 73 I’m not going to learn a new game," he said.

‘I’m Disappointed’

Omega, based in New York, returned an annual average of 11 percent from inception in 1991 through 2014, according to an investor letter. Cooperman’s fund has struggled lately; it lost 10.4 percent in 2015 and was down 5.6 percent in this year’s first quarter. He said that, after seeing clients pull capital amid lackluster returns, he’s running his fund as though it were a family office, since 40 percent of the money is now partner capital.

His comments came after Roslyn Zhang, managing director of China Investment Corp., the nation’s largest sovereign wealth fund and a big investor in hedge funds, criticized the industry for lackluster performance in recent years. Hedge fund managers are among the highest paid in the finance industry, traditionally charging 2 percent of assets as a management fee and 20 percent of profits.

“Over the last couple years I’m kind of disappointed by the performance,” Zhang said Wednesday at the same conference, adding many funds had crowded into the same trades.