Capitalism doesn't work when you design it not to. IMHO Tsipras is representing a good position, but probably for the wrong reasons.
Not markets or even free-markets but the construct of international commerce may not be compatible with greek life they should have the ability to opt out. Austerity has not been shown to work, The IMF and world bank have never fixed a country. Maybe the greeks will adopt a scandinavian model empirically that has been shown to increase most rational metrics of success. The cold war is over every where but fox news we no longer need to fear socialist bugaboos.
Rational limitations of the market and a social safety net has never ruined a country. well as long as you discount C.I.A. coups.
I agree that austerity doesn't work; the proof is self-evident. But capital markets have proven to be the best way to maximize wealth. Setting up good regulations to ensure less wealth aggregation is a political problem, not a problem with capitalism itself. Greece should have the right to assert its own sovereignty. Right now they are being tyrannized by the Euro. They could leave, but that won't solve their problem. They devalued their own currency many times in the 20th c, and it didn't solve their structural problem. There is nothing remotely fear mongering about saying that communism does not (cannot) work. Its just a fact, borne out by history. The Chinese only became prosperous when they shifted to a capitalist model. They are communists only nominally.
"socialism" or even communism in Greece or nearly anywhere is not going to resemble the soviet model, thank heaven and thus we do not need to fear it. I don't buy the capital market thing to me it seems not being the victim of an extractive economy is the best way to get rich. :)