The problem is, if one company dominates search, you have no way to evaluate whether they are doing it well.

You could just go to other search engines and run the same queries and compare results.

For example, I did a search on 6 different search engines earlier today looking for a specific Reddit thread related to an update to a certain Skyrim mod without quite naming the mod (because I couldn't remember the exact name of the mod, and was hoping to find the Reddit thread to get the mod name or Nexus link). All 6 had the Nexus page for the mod itself within the top 3 results, and all of them but Google and Yandex had the Reddit thread in question on the first page.