Personally, I find DDG gives me the best results of all the engines I've tried, including Google. But plenty of other people have different experiences. My hypothesis is that it depends on what you're searching for and how you write the search query.
Much of the problem with Google is that it's trying to make a guess about what I /really/ want, when what I really want is to find sites that contain certain words or phrases. Tracking me is irrelevant to that task, and if my online behavior affects the search results I get, that can't improve things.
I don't want a search engine to find me answers. I want it to search for web pages.
I like DDG because it (mostly) does what I want a search engine to do.
I'm not really bashing Google here, it's just that Google is a tool that accomplishes something different than what I need accomplished.
If I'm searching for something, it's very likely to be something a bit unusual for me to search for. If it's in line with what I need regularly, I don't search -- I go to my bookmark library.
I think the extent of this depends on 1) how long you've been using their search and other products, and 2) how much your interests diverge from the "average".
Either google engineers have really started to dig w3schools or they don't eat their own dogfood any more.