The last person to write an epic in Latin before Virgil was Ennius - and his style is nowhere near as sophisticated as Virgil's. What Virgil is trying to do is to take a Greek style and adapt it to latin poetry: that's a poetical statement, not a political one.
Consider also the magnificence of his character analysis and depth of appreciation for the minutiae of life. I'm doing Book X for A level - a massive part of that is a discussion of the meaning of pietas, mercy in warfare, what war does to people, ideas, social mores... It's an analysis of life, death and the transition from one to the other. Very little of this is even indirectly relevant to the propaganda point, let alone necessary to prove it home.
The political element does run through the Aeneid, but it would be just as valid if you ignored it: say, you had no idea who Augustus was and what all those references are to. The politics/propaganda *is* valid, and is very important to the poem, but I wouldn't say the poem hinges on it. In fact, I'm inclined to claim something like Virgil used Augustus' patronage to get publicity (and funding) for his work - in return for that, he had to write in some propaganda, which he may even have believed (after all, a lot of it just extols Aeneas as Father of the Romans, and you have to make the jump to it extolling Augustus as descendant of Aeneas) - and what's wrong with a little patriotic feeling in a poem about the foundation of your nation? After all, part of a Roman's pietas is loyalty to his country; so why would Virgil be immune?