[nl]

a parse tree showing which less-important words/phrases describe higher-level words

Things lower on a parse tree aren't less important than things higher. It just represents a dependency relationship.

[vtempest]

You're pointing out what's already obvious. You still need some way to find what's "less important", which is what the topic is all about, like by using grammar dependency or keywords infrequency.

[nl]

I'm not trying to be hostile, I just don't understand what you mean.

You still need some way to find what's "less important", which is what the topic is all about, like by using grammar dependency or keywords infrequency.

I have some experience in this area[1]. I found keyword frequency worked quite well.

[1] https://news.ycombinator.com/item?id=12356133