Eh, the only kind of server that I think you absolutely need full networking (address, iptables, routing, maybe even DNS) to be “meaningful” would be a database replica. Anything else, there is full use to partial network configuration: anything small enough that lets in a network connection someone else can use to diagnose (eg.: you can have a server that can spin up a meaningful session with only address and netmask, not routing).

That said, I’ve never seen a server, with or without systemd, set to wait for all possible network interfaces that are present to be fully configured… would me emotional murder with something like wireguard that by necessity has a depends on another interface’s routing. Usually with just lo plus any one available interface, it tends to suffice.