I recommend reading the actual paper. DDG is actually by far the worst by their measures. Even though Google has gotten worse, it's results are still massively superior to the competition. 9% spam compared to 31% for DDG and 23% for Bing. That's a huge difference.
I would recommend trying a SearXNG instance if you haven't before. You can combine results from multiple sources. I use Google as my main source while also having access to the DDG-style !bangs.
But whenever I need to search more in-depth, I use perplexity.ai
It makes the comparison for you and summarises, also gives links to where that info is found. Makes it way easier to find the more obscure information. But it is too slow to use for everything.