I don't see why. The main problem for exit is guaranteeing the availability of certain basic commodities that need to be imported - oil, some foodstuffs etc etc. So you'd need deals with - Russia and whoever in place. Then you issue a new drachma, it plummets in value and you instantly have the cheapest holiday destination in Europe + the cheapest exports of olive oil and whatever else Greece sells abroad and you'd get pretty much instant pick up of the economy. Crucially for a left govt, the benefits would go most rapidly to those currently out of work while many of the costs would land on the rich who would be making profits in relatively worthless drachmas (at least worthless outside of Greece where they currently stash their assets).
That's a tad simplistic but in essence it's what countries like Spain and Italy did through the 60s.