At least I think it’s gone…
Rabbi Yaakov Kamenetsky in his “Emes Leya’akov” on Pirkei Avos p. 67-68 argues the new decree of “אין קורין לאור הנר” arose only due to a decrease in awe for the laws of Shabbos over time. Likewise, differing customs are due to the needs of different eras and locations. This is why each locality must respect its own customs even though they are unique (unless the minhag is halachically improper). See inside.
Rabbi Kamenetsky adds that the local minhag (instituted by rabbis, says he) in some places against wearing Shabbos clothes on Shabbos Chazon was due to the decrease in mourning in those places for the Churban because the Jews there were rich and at peace. And Vilna was different, so the Gaon changed the custom.
In my humble opinion, it seems there is an actual prohibition here, above time and space. The Gaon was, of course, more interested in Talmudic truth than justifying “מנהגי פוליש”. Why even assume an empirical difference in wealth between davka Vilna and ALL OTHER places in THAT EXACT generation?!
(We have written of a slightly better approach to the topic by the Aruch Hashulchan.)
Jewry’s debt to the Gaon and his followers is unpayable.