Robert Reischauer, former CBO director, summed up the complaints from the left about Medicare Part D:

Initially, he said, people were worried no private plans would
participate. “Then too many plans came forward,” Reischauer said. “Then
people said it’s going to cost a fortune. And the price came in lower
than anybody thought. Then people like me said they’re low-balling the
prices the first year and they’ll jack up the rates down the line. And,
lo and behold, the prices fell again. And the reaction was, ‘We’ve got
to have the government negotiate lower prices.’ At some point you have
to ask: What are we looking for here?”