This is clearly not true. For example, the Pythagorean theorem is an old, completely leak free, abstraction with no computer required.
Sorry for being pedantic, I was just curious what you mean at all. Language as abstraction of thought implies that thought is always somehow more "general" than language, right? But if that was the case, how could I read a novel that brings me to tears? Is not my thought in this case more the "lossy abstraction" of the language than the other way around?
Or, what is the abstraction of the "STOP" on the stop sign at the intersection?