Dear Youdont,
Look in that very teshuvah and he writes that he was told off for using that sevarah. The poster on the first page wanted to use that specific idea that Rav Moshe and Rav Aaron completely rejected. And none of the previous poskim entertained. It would throw out the whole mesechtes eruvin. Good Yidden don’t throw away mesechtos or invent new ones. If we are to build eruvin in cities there is a whole list of precedent on how to do so. To just do a run around on the whole topic, when we have more resources than we did in the last millenium is too deviant to have a place in any form of Orthodoxy. Conservative Jews built those kinds of eruvin before they all started driving on Shabbos. This was Rav Moshe’s concern more than anything else. In his amazing foresight he saw that Brooklyn would be the battleground for the pseudo halachic eruvin.
If you want to discuss the actual nuance of eruvin, I’ll try my best. But you can’t just quote one liners. We would have to establish what was the general precedent all over Europe and how the postwar generation transplanted it to America. And then we could examine Rav Moshe’s take. I concede that there can be a kosher eruv in Brooklyn. But anybody who cares about authenticity knows that it would have to be under the auspices of a qualified Rav who can attest to it’s proper construction and that it is frequently checked.
To my knowledge, Rav Tuvya Goldstien was one such example. Though he explicitly said that it does not conform with Rav Moshe’s opinion. Are you claiming that it does?