I still have no idea what point you are trying to make. I have not claimed to be an expert on the topic, I only asked why no one can be an expert.
It sounds like your view is that no one can be an expert on disinformation because some topics are disputed. That's an "interesting" take. I guess that reasoning would leave pretty few experts in the world.
Saying they are experts are like telling you who is sexy or not. It's subjective. Some people really consider Marx or Friedman as the truth for instance. Digging deeper in the weeds we can make claims either way.
Experts are often self appointed as well. If I was to declare myself an expert in an obscure area you don't understand by making wild claims that sound plausible it would be hard to say I wasn't and if some peers accepted it it would be even harder to deny it.
An expert shouldn't be self appointed and if nobody trustworthy calls someone an expert they shouldn't be considered one too. If you consider someone an expert on your own by their knowledge it's different.
Other than the fact that "disinformation expert" is a fake expertise invented to facilitate fallacious appeal to authority in the void left by a distrusted press:
There are two answers to your question.
First, everyone attempts to derive the truth from imperfect information and therefore is a "disinformation expert".
There's no consistently guaranteed information access that makes any one person consistently an expert above most others, including Joe at his coffee table.
That type of access and divulsion used to be assumed of the MSM. They destroyed their trust, and so now "disinformation experts" demand that trust. Broadley speaking, they won't get it. And they shouldn't.
The second reason is that comprehensive presentation of any truthful information requires a presentation of all facts regarding it. Aside from the most mundane fact checking tasks, I've broadley observed "fact checkers" disseminating disinformation as much as the MSM does. Whether the method is lying by ommission or another.
It sounds like your view is that no one can be an expert on disinformation because some topics are disputed. That's an "interesting" take. I guess that reasoning would leave pretty few experts in the world.