Have a look at full mesh VPNs like:
https://github.com/cjdelisle/cjdns
https://github.com/yggdrasil-network/yggdrasil-go
https://github.com/gsliepen/tinc
https://github.com/costela/wesher
These build actual mesh networks where every node is equal and can serve as a router for other nodes to resolve difficult network topologies (where some nodes might not be connected to the internet, but do have connections to other nodes with an internet connection — I work with networks like that every day).
Sending data through multiple routers is also possible. They also deal with nodes disappearing and change routes accordingly.
tailscale (and similar solutions like netbird) still use a bunch of "proxy servers" for that. You can set them up on intermediate nodes, but that have to be dealt with manually (and you get two kinds of nodes). You also have to create routes for the node to be able to access the control server.
