I use a very basic statistics plugin that tells me, among other things, where traffic to this site originates and i'm a bit surprised that most visitors are still using Google which accounts for more than 70% of the referrers.

Unfortunately Googles' search engine and index is still one of the best, even with the censorship and result manipulation that takes place. I think that's pretty sad, but i don't know of any other search engine that compares to Google for general searches. However you need not use Google directly if you value your privacy. As a matter of fact, many of the so-called 'alternative' search engines, including DuckDuckGo, Startpage, Qwant, etc., use Google and/or Bing, so while they are not true alternatives, at least they insulate you from the attacks on your privacy that engines like Google and Bing present.

So stop doing that! Stop using Google directly and instead consider one of the many alternatives. I keep an updated list of privacy friendly search engines right here.