Globally routable doesn't mean you don't have firewalls in between filtering and blocking traffic. You can be globally routable but drop all incoming traffic at what you define as a perimeter. E.g. the WAN interface of a typical home network.
The concept is frequently misunderstood in that IPv4 consumer SOHO "routers" often combine a NAT and routing function with a firewall, but the functions are separate.
The concept is frequently misunderstood in that IPv4 consumer SOHO "routers" often combine a NAT and routing function with a firewall, but the functions are separate.