I have read quite a few Mahayana Sutra and if I were to generalize the template in which the Sutras are composed (although any generalization is bad), it would be something like:
"This is the best Sutra...
If you copy and recite this Sutra, such and such are the benefits...
...Such and such Bodhisattva attained enlightenment through this Sutra...
..finally a chapter here and there talking about morality (or in some cases doctrinal points)..."
In most cases, more than 70% of the Sutra's content is about the value of that Sutra and its benefits. Could it be that it was composed this way because early Buddhist teachings (Sutras) were supposed to be preserved in memory through recitation and the inclusion of this part makes it easier to memorize?
Or, could it be that the Sutra is teaching "emptiness"? Something like
Q. What is the best Sutra?
A. "This is the best Sutra. Preserve it and propagate it. Here ends the Sutra."
So is it really the "emptiness" of any doctrine that is the doctrine being conveyed in the Sutra?
No offense, but since I do not have any real Buddhist teacher around, I study (and often practice) on my own. And because of this confusion of the Sutras, I find it much more reliable to refer to the commentaries of Buddhist masters instead of relying on the Sutras themselves.