without massive transfers
Those transfers did in fact happen via the cheap loans that Greece received after entering the Eurozone. Greece could have used the money to modernize its' country. Instead the Greek government blew it on vanity projects like the Olympic games or to bribe voters. Let us be completely candid. Greece was driving towards disaster before it joined the Euro, because the structural problems were already there. Joining the Euro only accelerated it.
Another thing to consider is that Germany was by no means the harshest creditor towards Greece. Especially the small, often poorer than Greece, countries of the of the Eurozone had a hardline stance towards Greece, and their approval was needed as well.
google.com/amp/s/amp.theguardian.com/world/2015/jul/09/poorer-than-greece-the-eu-countries-that-reject-a-new-athens-bailout
Thirdly, the Greek governments, particulary the Tsipras government, was not helpful in finding a solution. The whole mess started when it was revealed that Greece had been systematically lying to its' partners, and it only got worse from then on. The Greek governments rarely upheld their promises and dragged their feet on reforms. And then there was this complete disaster that the maniac Varoufakis caused. None of that helped Greece's negotiation position.
Finally, Greece did in fact made some incredible advancements in e.g. reforming its' bureaucracy. As a Greek government report said, they made more progress in the time 2008-2018 than in the three decades preceeding it. But that also highlights how far behind Greece was. I mean they did not even have a central registry of the landowners in Greece, no wonder nobody paid landowner taxes. Even most African had one at this point.
German banks
Aside from the fact that French and Italian banks were actually more exposed to Greece, it is worth noting that most of those loans were made on a sound base, going from the knowledge that was available. The banks looked at the evaluation of Greece via the ECB, which was based on the (falsified) numbers provided by Greece. There was no way of knowing that Greece would be lying so brazenly about its' deficite. Again, Greece is not the helpless victim here. They actively asked for loans and even cooked the books to get them.