At what point do we also blame cisco customers for just plugging stuff in and not changing passwords? Cisco did not come into their customers locations and set up racks of stuff, or did they?
If this was just unsecured, internet facing routers then your point would make sense. However, in this case there is a vulnerability in the WebUI platform that allows unauthenticated users to make admin accounts to the system. That is absolutely Cisco's fault
If a fresh deployment isn't secure out of the box, that's definitely on cisco. There's a lot of people out there who just plug in some hardware and then use the GUI to configure it. Just because it's best practice to turn it off, doesn't mean everyone is skilled enough to do so.
We did have one compromised router from this at work, a fresh deploy that someone did a while ago and then the project got put on hold before it was actually configured. Was just sitting there with a public IP not doing much, but sure enough it was owned when I looked.
One interesting thing is that the machine had HTTP enabled, but we had locked down SSH already. In the config you could see the attacker tried to enable SSH but couldn't get it working (subnet inverted, lol cisco).
On a home network, I like having the web UI enabled for local access out of convenience, and I like buying higher end networking equipment. I don't enable it for external access though, that's just asking for trouble.
It makes absolutely no sense in an enterprise environment, but there are a non-trivial number of non-enterprise customers of enterprise equipment.
On Monday, Cisco disclosed that unauthenticated attackers can exploit the IOS XE zero-day to gain full administrator privileges and take complete control over affected Cisco routers and switches remotely.