The Google search engine didn't have anything to build off of when it was introduced since it was using an algorithm and not ML. You could create a search engine today without utilizing any click data outside of "what link did this user click on the result page and did they search for a similar query or try another link as their next action".
In fact, this is already happening. DDG is building its own crawler (I often see the ddg user agent on my web properties) and they don't have any open "machine learning expert" positions.