"He can certainly sing, and I'd like to see a bit more personality when he's singing," the Idol executive producer toldOK! Weekly in a Wednesday report.
If the 25-year-old winner does find that charisma, Lythgoe said he might someday rival the success of former Idol fifth-season finalist Christ Daughtry.
"[Cook could be] enormous for a long time," Lythgoe told OK!.
Lythgoe added Cook wasn't the only seventh-season finalist who could use a boost of character.
"That was the only thing that I think our finalists lacked a little bit this year, was more charisma," Lythgoe told OK!.
Idol finalists weren't the only people Lythgoe apparently has a problem with, as he also took aim at President George W. Bush.
Lythgoe claims Bush's "people" insisted the President participate in Idol Gives Back for the second year in a row despite producers being disappointed at Bush's lack of effort in fighting poverty.
"The President is always saying 'I want to be on [Idol Gives Back],'" Lythgoe told OK!. "We didn't ask the President this year to say anything because we are all a bit embarrassed about him, and the office insisted that, because the [primary] candidates were on it, the President would like to come on and say 'Thank you.'"
Lythgoe said he plans on continuing to help those in need through his capacity as a So You Think You Can dance judge and producer by having audience memebers donate canned goods before entering.
"So if you want a ticket for So You Think You Can Dance, all you have to do is bring a can of fruit or vegetables or something," he told OK!. "And I'll come and collect it each week and just take it away."