Pages 5.2 is severely lobotomised, as such it simply can not do a lot of the previous templates.
Install iWork '09 and update it to v4.3:
Templates are stored in the respective Pages application. I just “borrowed” a Lesson Plan template from Pages ’09, and put it among my custom Pages v5 templates. Pages v5 would have nothing to do with it. This is a perfect example of Pages ’09 as a feature superset to the current Pages v5 implementation.
Did you try expanding the Captured pages first?
I know that is not a real solution, nor as useful, but at least you might be able to open it in Pages 5.2?
They gave some reasons, such as need to have parity with the inferior iOS version and to be able to more faithfully copy the files over iCloud, but since so many more important features were tossed overboard and without notice, I'd say it had more to do with internal Apple corporate manouvers.
Either way, bad news for users who were ambushed on this and still are.
The simple fact is the new format is unreliable and incompatible with just about everything else except itself. Best avoided.