I think what you said is true. Of course it was a mistake to let Greece in that early. Nevertheless I think that overall they made the right choice.

These decisions ware made immediately after the cold war ended by representatives that were raised by parents that killed each other in a world war. European integration and the Euro are highly connected with the 2 + 4 talks [0] and German unity [1]. Europe would look very different if these politicians had not taken the risk and united it.

[0]: https://en.wikipedia.org/wiki/Treaty_on_the_Final_Settlement...

[1]: http://www.spiegel.de/international/germany/the-price-of-uni...