It's actually not just because of that and it's not as simple as "it's just because of fixed budgets". The fundamental problem just like with most places there is in fact corruption(there is a lot to talk about here actually), and a decades long misunderstanding of basic economics. I.e. until 2019, which is when I finally gave up on it, most people in leadership for decades fundamentally disagree that it's unsustainable that the budget is not balanced. I.e. the money that comes into KV's from insurance and the money that is being paid to doctors is not balanced.
First of all the fixed budget don't apply for everything, there are budgeting hierarchies. Radiology for example is not limited at all. First radiologists get paid whichever amount they want.
Second, when migrants flooded the healthcare system the following happened:
- The political leadership of Germany had a meeting with the political leadership of the healthcare system
- Due to the lack of technical competence on the side of the political leadership of the healthcare system they threw the migrants into a special accounting bucket. I think it was 4, but I don't fully remember
- The accounting bucket was chosen mainly because the custom made accounting system had been built over decade and most of the knowledge about it is either retired or dead and no political leader wants to invest in changing it, because nobody wants to be responsible if there is a problem with doctor payouts for one quarter during a migration.
- The leadership of the KVs were too scared to touch their own accounting system and as a result searched for an accounting bracket to dump migrants in.
- The only two states that were competent enough to build their own that is easy to change were Schleswig-Holstein and Bavaria.
- The migrants are outside of fixed budgets due to the special status are in, meaning that if a German retiree goes to the doctor the second time at the end of the month the doctor is not paid, but if an asylum seeker goes 10 times the doctor gets paid in full 10 ten times. It creates an imbalance in who certain doctors would like to treat.
During one of the sessions with the policymakers in Hamburg the leadership openly said that they would like it to be more like the dentist situation, where only basic care is covered and the rest is paid in private.
You have to understand that German retirement money can be as low as 40% of your last working salary, which is extremely low for most people and it's the lowest of all of western Europe. Although I imagine that after this whole evaporating European wealth for Ukraine the situation might end up looking even worse in other places of Europe.
The whole situation is completely avoided, but the political leadership has been systematically blocking attempts at solving the technical challenges. They have inherited a system that was built for a completely different demographic of Germany decades ago and have refused to reform it, because they are extremely scared that they would lose the support of the doctors that elect them.