Eruv originally meant wall and those are the main functions of a wall. It is reasonable to assume that that is why the law used a wall as a condition for exceptions on Sabbath restrictions. They sure as hell didn't originally use a freaking WIRE.

It seems similar to Islam allowing women to wear completely sheer niqab.

Agreed. I think in situations of religious laws, where the text really can never be changed because it is literally holy, it's at least understandable and mostly harmless. But in general I find the practice of reinterpreting law texts to the point of absurdity really problematic. It undermines faith in the legal system, because suddenly law texts become "legalese" that cannot be interpreted by laymen. In the worst case, you get "creative reinterpretation" of legal terms like the Trump admin is doing it currently.

I remember reading about an US state where the governor was allowed to unilaterally modify state laws before they came into effect, by removing parts of it. The constitution didn't specify what was meant by "parts", so some governors took it as the right to delete individual words and letters from the text and thereby completely change the meaning of the laws...

Non-jew here, but what would be the rationale for the shabbat exceptions otherwise? I assume they didn't just make up random rules for fun.