However, now that you've brought it up, possibly outside of material science, every invention in the history of engineering falls under the description of "old elements doing old things producing expected results". Taking that quote out of context misses a very important question: was it obvious beforehand that such a result was desirable enough to put those elements together?

The answer to your question of "what's novel" is, literally, the combination of elements and the difference it presents over prior art. However, at a higher level, what this quantitative approach misses is this: slide-to-unlock provides a convenient, usable and visually appealing way to unlock a phone. You'll note that these adjectives are some that Apple users regularly attribute to Apple products (since before the iPhone!). These qualities are arguably a primary reason for their success.

Sure, when boiled down to their implementation, they don't look so impressive, yet few others are said to match Apple's level of polish. Why is that the case if such features are so easy to implement? Maybe because the feature itself is not obvious. Such qualitative aspects are not always apparent from looking at the claims alone.