And, no, I don't think it's practical for everyone and their grandma to "just set up a bastion"
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.
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?