rel="canonical" tag on every page

Looking at the reports generated by Google Search Console I have attempted to correct some of the reasons for pages being determined as non-canonical or excluded from the Google index for a number of reasons.

In addition to my page of Canonical URLs, this page discusses the notion that ALL pages should have a rel="canonical" link tag.

Only one Canonical declaration seems to be the key

When you think about it there can only be one page that is truely "Canonical". Duplicate content aside, if you are following "guidelines", your pages should be unique. A duplicate URL is a different issue.