If you use the quick search feature on the top right, the results will be from years ago (most likely "relevant") rather than the most recent.
How can this be set to return most recent results as default?
Short answer probably is that it can't - it's a quick search. For most recent posts or posts after a certain date, you have to use the full search. Doesn't take much longer and is often quicker than scrolling through old, irrelevant posts.