Keynesians advocate for large amounts of public spending during recessions to stimulate the economy. They don't advocate for racking up a large amount of public dept to spend during the periods of growth, which is what happened in Greece.

There are many other issues with the Greek economy such as clientism, the inability to collect taxes, etc that all economists would agree needs fixing.

You're are caricaturing. that's not what Keynesians say. Spending to stimulate growth during a financial crisis ? sure,that's what the USA just did. But not spending just for the sake of it. And bailing out private banks with public money is not Keynesian-ism. It's moral hazard.