So, in other words, these models were specifically made for and distributed by an ISP, and were not off-the-shelf models. The backdoors were there for the ISP managers.
Well, I trust my ISPs router ... well, not at all, actually.
Because I assume my ISP is either incompetent or dishonest, I don't really care which, I simply don't trust them. And I sure as fuck don't trust them with access to my actual network. I want a layer of security between me and their shit, because I assume their stuff is trivially hacked.
My wife and I each have our offices set up where our own router is getting DHCP from the ISPs router, and then firewalling everything from it. We each have our own locked down wifi, and entirely separate networks. I'm pondering a third router to provide the guest wifi.
Other than disabling the ISPs wifi and using our own, I wouldn't even know the SSID or the password for the ISPs crap. I assume they haven't turned it on without asking, but I never check -- come to think of it, I'd have to find out how.
My parents and my in-laws have routers we've bought them to sit behind the crap the ISP provides. Because I know for a fact that in both cases the ISP provides a router with default wifi SSID and passwords which are published in the docs they give you.
Because it's printed in the "how to" for every damned subscriber, and you can't change it, you can pretty much imagine that if you find an SSID of the right name you can connect to it, and probably have management access to it.
For 99% of network users out there, these vulnerabilities are of no practical concern.
But the problem is so many households trust that the wide open, back doored, well known remote-admin credentialed, shitty routers they've been provided with give them any form of security.
Which means for the overwhelming majority of home users who aren't tech savvy and paranoid, these vulnerabilities are absolutely of practical concern ... because their PCs are directly plugged into the ISPs router, or they're using wifi from the ISPs router.
I'm betting a lot of home users figure they have the router from the ISP, so they don't need anything else.
That these are ISP models doesn't diminish the number of people who could be impacted ... it greatly magnifies it. Because most people who don't know better (and a few who do) connect their PC directly to the ISPs router.
Honestly, go talk to a random neighbor .. see if they have anything between them and their ISPs router. My best is they don't.