There at least was this thing in the past that lets me question their good intent (and/or competence): https://www.derstandard.de/story/2000118461444/privacy-browser-von-duckduckgo-plaudert-besuchte-webseiten-aus
(only in German)

Besides that, it is still a private Company that has to find ways to fund itself, so might have an intent to not always prefer the less-profitable option that would be better for the user.

I use their search engine, but would not consider the browser as there exist less commercial and less restricted alternatives (mainly FF and its derivatives)