Let me make something clear. I won't discuss any bugs that DDG had in the past, has right now or will have in the future. Every piece of software has bugs, missing or incomplete features and so on. I'll just skip those as those are fixable, given enough amount of time, man power, or other resources.
What I'll be focusing in this post is why the idea/concept of a search engine that doesn't track people won't work.
That means that DDG will do the opposite of what Google does when you search something. If you don't know how Google works, let's just say that they save the query terms you use when you search something in Google and use those to make a personal profile (sort of) that is used later to show you targeted ads, better results based on your search history and who-knows-what-more.
So... I already wrote a few paragraphs and I still haven't said why will DDG fail. Well, it's pretty simple. It will fail because we are different. No, really, let me explain.
By now Google already knows that my main interests are developing, motorbikes and
When I search "Shark", I'll probably get results about the motorbike helmets company, which is also fine because that's what I'm probably looking for.
When Bob, who is a biologist, searches for "tree", he will get results related with nature, because that's what he is probably looking for.
On the other hand, DDG, which doesn't know what are my search preferences, will give me results that don't make any sense for me.
DDG will do it's best to match the words I wrote in the search input field with all the pages they have indexed, trying to look for matches at the most important/relevant parts of each page (title, short description, etc...). But this just isn't enough.
That's how search engines used to work 7 years ago. And lets be honest, we didn't get the results we were looking for on page one. We had to use more words to describe better what we were looking for.
That's the main reason why DDG will fail. The search engine itself is doomed because it won't be able to deliver the right results.
One possible solution for DDG would be to actually track users and give them better results without sharing that tracking information with 3rd parties. That way users would be able to benefit the accuracy of the results while not worrying about their privacy.
Maybe even let every single user choose if he wants to be tracked to get better search results or stay untracked and get the "default" results that everybody gets right now.
One thing is clear. Current DDG strategy won't lead them to be the search engine, a title that right now is in Google's possession.