This is stupid clickbait title, and the article isn't even very precise. Yes, that whole fritz.box situation is known and bad. But the problem discussed here doesn't nearly apply to every situation. Specifically, the box's builtin resolver (which is still used by default by a lot of things) knows not to forward fritz.box requests to the outside. That is, `dig google.com.fritz.box` and everything else say NXDOMAIN when you're using the builtin DNS.
This has made much faster systems not being able to process packets at line speed. A classic was that standard Gigabit network cards and contemporary CPUs were not able to process VoIP packets (which are tiny) at line speed, while they could easily download files (which are basically MTU-sized packets) at line speed.