For the vast majority of people, which DNS their network uses is an afterthought, and by default, it’s usually set to the one their ISP runs for them. That’s not a bad thing, but most ISPs select their DNS server for ease of support if something were to go wrong with your connection, not because it’s the fastest or most impervious to outages. Changing it on your devices one-by-one can take up a good chunk of your time, and it’s not even possible to do so on some devices. The best course of action is to change it at the router, and it takes just a few minutes to do so.