You raise a very good point. I think there are several ways this can be caused, some of which you already mentioned yourself:

1. Our definition of knowledge is itself subject to the trilemma. Every statement we make about not-knowing is just as much in need of a dogmatic assumption, an infinite regress or a circular reasoning as statements about knowing. If we take apart the statement “We do not know anything”, we will find that multiple of its parts are based on the assumption, that something exists, which itself is a textbook example for the trilemma. Thus we can not know that we do not know anything, while at the same time knowing, that we can not know anything.

2. The subject matter of paradoxes is imaginary. Does the sentence “This sentence is a lie” really exists, if it is entirely located in a latent space of common understanding? What makes it be a thing that can be referred to? Our reference can only be made into this latent space of linguistics and common understanding, but this applies to every piece of knowledge.

3. Logic theory doesn’t hold up when faced with self-reference, which would be better dealt with using unconventional logic systems like Paraconsistent Logic.

There are probably more…

I would really appreciate it if you could recommend me some resources(book, video, podcast, anything…) on cognitive closure.

Difficult. There are many different concepts of cognitive closure and some may be more to your liking than others. I personally like Kant’s approach in Critique of Pure Reason. He introduced “categories”, which are mental frameworks that shape our understanding of reality, and argued that certain aspects of reality may be inaccessible to us, because we lack the categorical framework for those.

On linguistic relativity, I highly recommend Guy Deutscher’s Through the Language Glass: why the world looks different in other languages. It’s an overview of the entire research within this field, which challenges every linguistic theory regarding how language shapes our understanding of the world and thus debunks “common” linguistic myths.

You really put effort in this, I don’t know how to thank. Simply put, you are awesome.

Thanks for mentioning about “The Münchhausen trilemma”, it is exactly what I was thinking about the knowledge. I will certainly do further reading about it.

You are welcome!