An eruv is not a kulah from the 1960s. It goes much further back – there are Gemaras that discuss it.
Eruvin 68a brings a story where Abaye was asked why there is no eruv in his town. Many meforshim (Birkei Yosef, Chasam Sofer, Avnei Nezer, and R’ Moshe Feinstein) use this Gemara as proof that there is actually an obligation for a Rav to make an eruv where it is halachically permissible to do so.
I don’t think people today treat them with no awareness.
Where I live, yes, I use the eruv. Do I trust the eruv? Considering that it’s not a person, no. But I do trust the Rabbonim who oversee it!
I don’t personally check the eruv. The local Rabbonim check it every week, and I rely on them.
I’m not sure what chumros of the past you refer to when asking if they were discarded, so I can’t really say.
To say that R’ Moshe was hesitant or opposed to “many” of the eruvin… I’m not sure what you refer to. Do you mean in places like Brooklyn or Manhattan? That is well known, because he felt it was not halachically permissible to make an eruv there. In places where it was permissible, he held (as I wrote above), that it was an obligation to make one. Obviously, it needed a knowledgeable Rav to oversee it, to ensure it was done correctly. But he wasn’t opposed to the idea of an Eruv.
I’ve been told that in Elizabeth, NJ, R’ Pinchas Teitz zt”l built an eruv, but was nervous that people would forget the halachos of carrying on Shabbos. Therefore, one week each year, the eruv was taken down. It was usually done the week after Parshas Zachor – since everyone came to shul to hear Zachor, he’d be able to announce to the entire community that the following week, nobody should carry, as the Eruv would be down.
