Context is important, and it's one metric amongst others that should be used.

The point is, there are clearly actionable points GA can offer. It's disingenuous to think there are not.

I agree, saying that there are no actionable points in GA is like saying analytics in general are useless.

Counter example: I search for information on a subject. I get many interesting and relevant results and therefore spend more time on the page.

This makes it even more obvious that a longer or shorter session length is not clearly better or worse, it depends on a lot of other things.