Illusion is a word that indicates something appears one way but is in fact another. It’s the very first word of the title and the article starts out explaining exactly why it appears to be an illusion.

The article doesn’t try to explain that there is a moral decline. And the title didn’t indicate that there is a moral decline. They deal with explaining why people report it despite it not being there.

> I think those conducting this research are poor students of actual history.

While it’s definitely true that people sometimes forget to read relevant material before they compose work of their own. There doesn’t appear to be any indication that this is the case neither with the title nor the content of this article. I would encourage you to reread both.