The problem with TCP/IP is the lack of a standard and robust VPN/overlay network protocol.
Everything we have is extremely fragmented and/or proprietary.
IPv6 is completely useless and doesn't solve this problem.
Normal people don't care if they have to pay 5 dollars instead of 50 cents to rent an IP address. This is a problem specific only to the huge providers, and we don't need to rollout a whole internet upgrade just to optimize a tiny part of the operational costs for huge providers.
We are trying to change that with OpenZiti - https://openziti.io/. Its an open source network overlay built with zero trust principles and deny by default in mind. We also built it for developers, so includes SDKs and other means to embed overlay networking directly into the SDLC.
It's a complex problem that hasn't even been formulated properly yet.
For example, every existing solution touts "security" and yet completely mangles the difference between authentication and encryption.
Authentication is important - you don't want random servers or users to enroll on your network, and you want good tools to rotate and manage secrets.
Encryption isn't important unless you care about state-level actors sniffing your traffic at the backbone. (And if you care about that then you already have your own datacenter.)
Meanwhile encrypting all network traffic is a huge performance penalty. (Orders of magnitude for some valid use cases.)
IPv6 is completely useless and doesn't solve this problem.
Normal people don't care if they have to pay 5 dollars instead of 50 cents to rent an IP address. This is a problem specific only to the huge providers, and we don't need to rollout a whole internet upgrade just to optimize a tiny part of the operational costs for huge providers.