And, no, I don't think it's practical for everyone and their grandma to "just set up a bastion"
There is a dramatic difference in effort between ( owning a device ) and ( owning a router, configuring network access to the device, then owning the device ).
Also psychologically: If I was a rock hard piece of shit and I knew I was at the doorstep of a personal device, I would treat it much more aggressively than a router. I suppose maybe that's just me and not the kids and enemy states.
edit: Changing the subject to insulting me is a bad way to conclude. You're creating an illusion the debate is concluded in your favor instead of responding to points. I don't think any of my points had a sound argument against them.
I have exactly one machine which needs to be accessible from outside the local network. The rest of them should never be. Do I want to spend extra time ensuring that each and every single device on my network is secure, or do I want to do the inverse and assume all devices are secure and only spend effort to make the one machine exposed?
I can't imagine anyone who would actually want or need their WiFi toaster to be publicly routable, WiFi cameras, every computer. There's absolutely no reason for it. Instead of relying on network isolation, we expect users to just implicitly rely on who knows how many different firewall implementations. Hopefully your router configures it by default.
If you could scan one million addresses every second it would take about 500,000 years to scan just one /64. Not sure how practical that would be.
When I was still with an ISP that did IPv6 my Asus would block any incoming connection attempt unless it was a reply (SPI firewall), though it may have (IIRC) allowed pings in by default.
You have a router, it has a firewall, that is meant to be used to control access to the network, you don't have to assign rules to every device you can assign default interface rules that apply to any connection.
Just because you get a publically routable address doesn't mean the internet defines physics and hops over your router and firewall.
Also as an aside - perimeter security is a very outdated way of looking at security, yes the perimeter is still important but if it is your first and only line of defense you are gonna be in for a bad time, defense in depth as it is called where you look at your systems and networks as layers to an onion is the more modern standard and NAT as a security mechanism has never been standard in either because it isn't.
Even then id still rather ensure every device is appropriately firewalled. 'not worrying about it's sounds like a hardened shell with a juicy center. What happens when a device does get compromised and tries to spread to your local network?