The inaccuracy of the time on page metric makes it less important. Conceptually it is an important concept but the way it is measured devalues it.
Time on page measures the difference between when opens a webpage and then clicks another link. Or opens a new tab and visits the same domain. A common fallacy is that time on page represents all users, when it only captures those that complete those actions. So it is not reflective of an overall audience. It tends to skew up.
Other measures like Attention are more important than time on page.