It's not an architectural problem. It's a fundamental issue with trust and distributed systems. The same issues occur in physical spaces, like highways.
The core issue is that hackers can steal the "identity" of internet customers at scale, not that the internet allows unauthenticated traffic.
> The core issue is that hackers can steal the "identity" of internet customers at scale
That's on one end, right? There's also the other end: as a user connecting to the network, currently one is subscribing to receiving packets from literally everyone else on the internet.
> It's a fundamental issue with trust and distributed systems
We currently trust entities within the network to route packets as they are asked. The network can tolerate some level of bad actors within that, but there is still trust in the existing system. What if the things we trusted the network to do were to change slightly?
The core issue is that hackers can steal the "identity" of internet customers at scale, not that the internet allows unauthenticated traffic.