Again, the perfect song tells a story, the more evocative the better. The instruments and melody are secondary, as long as they complement the lyrics and mood. Just my opinion.
This one I disagree with if only because classical music and post-rock are a thing. For centuries people were telling stories through music without vocals, and continue to do so today. But as you said, it's just your opinion. We'll have to agree to disagree on this one.
That's fair! As far as post-rock goes, I've never found it "perfect." It's certainly very expressive -- EitS, GY!BE, Steven Wilson, etc -- but I don't think perfection is the right word (nor do I think post-rockers would exactly want their music called perfect, but that's a separate issue). Further, alyrical music can tell a story just as well as lyrical, if you listen hard enough. I was ignoring classical for the sake of the post. Beethoven's Ninth is the pinnacle, it really is, but it's not what I'd call a song per se.