People don't believe QAnon, or that Bill Gates created COVID-19 as part of his secret plan to implant chips in everybody, or that 5G towers caused COVID-19, or that the earth is flat, etc., because they do not have access to the tools to find and critically evaluate the refutations of those idiotic beliefs.
All the necessary tools are readily available on the internet. But using them takes more effort than they want to put in. And if they do put in the effort to think critically about something they saw on social media, there are dozens more to take its place.
The falsehoods can be designed to be entertaining and to appeal to the fears and prejudices of their targets. This makes it easy for someone to get into it because they can start out just for the entertainment. They aren't going to seek out opposing views and critical evaluate them at that point because it is just entertainment. Somewhere along the line, it changes from being just entertainment to something they actually believe in.
There is a societal change that needs to take place to fix that. Not caring about truth is a sign that a person has given up, it feels like a lot of people have given up.
It's not about countering falsehoods, it's about giving people the tools to think critically and not be duped by falsehoods in the first place.