1) Is it easy for a somewhat technical person to change? 2) If you don't mind telling, who's your ISP?
Given the quality of MSFT's and Apple's firewalls, and the ease of use of MSFT's (I assume Apple's is easy to use, but I have no direct experience), I cannot agree that a default DENY firewall policy is a good default configuration. We'd be back in the world where consumers would need something uPnP to manage firewall rules on their router.
I can agree that refusing to route requests to things like port 445/tcp is reasonable.
The router is an AVM FritzBox 7340, the ISP is Snap (New Zealand).
I have no idea if this setting is common or not for IPv6 deployments.
Do you know if you can set that FritzBox up to just act as a DSL->Ethernet bridge and pass through packets to another device that does all the routing? (Sorry if that doesn't make sense. I'm not a professional network nerd, so my terminology might be confused.)