CNBC commentator Ron Insana isn't too impressed with the Federal Reserve's latest policy statement, in which it removed forward guidance, leaving it unclear when it will raise interest rates.

"The Fed has muddied — significantly — the outlook for monetary policy," he writes in a commentary for CNBC. "This is as unclear as I have seen Fed policy in quite some time, and it is not helpful."

Many economists expect the central bank to begin increasing rates in September. "My guess is that a rate hike is not in the cards in June, and maybe even in 2015 altogether," Insana notes.

The Fed has kept its federal funds rate target at a record low of zero to 0.25 percent since December 2008.

In addition, "it is not at all clear that growth is reaccelerating in the U.S.," Insana writes. Indeed, the government reported Wednesday that GDP grew only 0.2 percent in the first quarter.

"If the Fed were to raise rates sooner, rather than later, growth slows further. If they wait, as I have long expected them to do, the dollar may weaken more, driving oil prices even higher and, thus, complicating the inflation picture even more," Insana explains.

"At this point, I am not sure any single outcome is assured. I haven't felt that way in quite some time."

Meanwhile, Harvard economist Martin Feldstein takes the Fed to task for its massive seven-year easing program, which a $4.5 trillion balance sheet, in addition to near-zero interest rates.

"The Fed's unconventional monetary policies have created dangerous risks to the financial sector and the economy as a whole," he writes in an article for Project Syndicate.

"The very low interest rates that now prevail have driven investors to take excessive risks in order to achieve a higher current yield on their portfolios, often to meet return obligations set by pension and insurance contracts."

The result?

"This reaching for yield has driven up the prices of all long-term bonds to unsustainable levels, narrowed credit spreads on corporate bonds and emerging-market debt, raised the relative prices of commercial real estate, and pushed up the stock market's price-earnings ratio to more than 25 percent higher than its historic average," explains Feldstein, chairman of President Reagan's Council of Economic Advisors.

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