If your smart toaster is saturating your bandwidth, it should show up as an expensive line-item on your bill. You should see that "SmartToast9000" used $80 of bandwidth, "baidu.com" used $17 because it used your bandwidth to ddos. And, of course, the tooling to catch these things before they escalate would likely become part of our computing devices.
Right now, everything is completely opaque to the end-user and we all suffer except for bad actors. It's a problem when we can't even estimate how much bandwidth we used in a month off the top of our head. Instead it should be informing our decisions from the IoTrash we buy to which websites we use.
Example: the internet was regularly awful at my girlfriend's house. We couldn't figure it out despite calling the ISP. On a suspicion, I helped my gf install a bandwidth monitor on her laptop. We found that a recipes website she often had open would get stuck in some sort of ad-loading retry loop due to her adblocker and would saturate her download bandwidth as long as she had it open.
It's completely ridiculous to me that there's no feedback built in to the browser when I think it should be a first-class UI component. I think transparent + metered bandwidth (at a fair price of course) would start the ball rolling on this kind of tooling. Until then, it's like everything acts like bandwidth is unlimited.