Considering the lack of competition I can't blame them for not trying. Why spend the money? Nobody is going to use Bing lol.
That said, my personal anecdata is that, a few years ago, g! Google search results would often find things that DDG didn’t - but today, those results rarely help (hence my OP).
I am not super confident DDG has got better, but it certainly feels like Google’s quality has diminished.