I noticed the change around 2007, with few houses having Christmas lights (and those who still had decorations up, had fewer). This trend has gotten worse since then, with wimpier and wimpier displays being the normal. Instead of competing to see who can decorate the most, the competition is to see who can have the wimpiest, lamest display of all.
Other aspects seem watered down. There are fewer Christmas specials on TV, and fewer Christmas songs in stores than only 15 or 20 years ago. For a while, they would start Christmas songs up, solid, the minute after Thanksgiving and continue them through New Year's Day. Not any more.
And I rarely see the types of Christmas advertisements and in-store displays that were so common in the 1970s. Where is that Sears Wish Book? I understand stores come and go, but why don't you see a Walmart Wish Book or an Amazon Wish Book? Or anything even remotely resembling such? And no, those 16-page inserts in the snoozepapers do not count. (Not that I would shop Walmart any more, since all they carry is rubbish.) I almost never hear of any major holiday events downtown, either--even in small towns, they had bigger Christmas displays in the mid 1970s than they do in big cities today (unless you are in New York City). But, at this rate, a small town in Montana or Idaho in 1975 would be better lit for Christmas than New York City in 2020.