at some point in between the two there's a 10Gbps link being shared between 5000 subscribers at peak times and now the bottleneck is 2Mbps per subscriber. This link may or may not be under your ISP's (or Netflix's ISP's) control, and it may or may not be the only relevant bottleneck.

No, that link is absolutely under Vodafone's control. They're deliberately not upgrading it so that they can extort money from Netflix.

The solution ... is content distribution.

CDNs have been worldwide, including Germany, for a long time. That's not the problem here.

There are two issues here.

If the CDN is so poorly interconnected with Vodafone that there's one bottlenecked link, then it's not really accomplishing its job, at least as far as "inside of Germany" is concerned. It might have reduced pressure on another bottleneck, like links between the US and the EU, but it still needs to spread out more. If Vodafone is blocking that, then pressure should be applied to force them to open up more connections. I'm assuming this CDN serves more than just Netflix, mind you.

Secondly, the question of responsibility cannot be answered the same way today that it was answered in the Internet of universities. Netflix and Vodafone are not peers. The bandwidth ratio between them is incredibly lopsided. This will never change, there is no foreseeable scenario under which Vodafone has a reason to send anywhere near the same amount of data to Netflix as it gets back. This asymmetrical relationship inherently implies a different kind of business arrangement than traditional peering.

What Vodafone (any ISP) provides to Netflix (any content provider) is access to consumers. This is a service, and services are not free. The natural monopoly ISPs enjoy implies some degree of regulatory restraint must be applied on them, but it does not mean they bear all the costs of all the infrastructure either.

However, my bigger point is that this cannot constantly be reduced to these two-party analyses. Netflix is waning, others are rising, this problem needs to be solved in a scalable way.