Quad9's a nonprofit, which may alleviate concerns about a profit motive. With that said, they do log some metadata and share statistics/"anonymized" query data with the companies that provide their threat intelligence.But what are the alternatives? Google, OpenDNS, Quad9? As far as know, none of them are even trying to commit themselves with privacy
As for an alternative with a focus on privacy, my choice would be CleanBrowsing.