While I have switched to DuckDuckGo a long time ago, there basically is no proof they're actually not doing exactly what Google does.
DuckDuckGo just put out a post criticizing Google for personalizing search results. They're a small company without many resources, and privacy has been their primary selling point from the get-go. Yes, DuckDuckGo could also be personalizing their own results, but if they were and people found out, there's risk of a significant outcry. Until I see evidence to the contrary, I'm inclined to assume good faith.
See also: discussions around "but how do we know for sure that Apple has better data privacy than Google?"
If you assume all organizations are equally ready to ignore user privacy, what do you use? Do you program your own everything or do you only use FSF-approved software whose source code you have personally examined and compiled?
It's all about degrees.
So your "there basically is no proof" is both wrong and a red herring.