They don't want you to know when to stop looking. If they present feeds "newest first", you can move on as soon as you get to an item you've already seen. With a "curated" ordering, you never know when you'll see new content, so you keep scrolling (and thus providing them your interest data and looking at ads).

This is a very interesting word. I think you mean insightful, which is what people usually use to describe a clever or novel thought.

I've never seen the word inciteful before, but that would probably mean something that really riles people up and makes them angry. After rereading your last sentence, it seems like you actually meant inciteful, but it's not a word that's used very often.