DDG is worse, at least anecdotally. But kagi is much better. Looks like the researchers didn’t study that one though so no “proof”, but anecdotally I completely stopped using Google for search.

That is still just one specific measure. They will also have a specific definition of what they consider spam. What I have found, admittedly anecdotally, is that the results just don't answer the search anymore. The results aren't spam they just aren't good.

DDG did have better results in one major instance for me in figuring out an error message that Google gave me literally no results. DDG has several appropriate answers that LED me to a solution. I don't think that will stay the case overall but Google does need to do better.

Other search engines can be worse, but if we keep using google and allowing them to have the monopoly, no search engine will ever get better.

I haven't done extensive research, but as it's a paid product, they have the user's interest in mind, instead of ad revenue.