I think it's hard to describe how one search engine is less good than another. It just... is. Quite often there are very few or even no relevant results for my query, and as soon as I put a "!g" in front of it I quickly find what I'm looking for.
Don't get me wrong, DDG works fine for me for 90% of my search queries (which are usually quite straightforward). But I have noticed a difference in quality vs Google, at the margins. I'm considering trying out Kagi.