I feel like anyone who already had a know-how to change their DNS will just change to one of the other hundreds of free servers and the people who couldn't be bothered to switch to google DNS will already have been "blocked". Or they are using a VPN already..
Or run your own recursive DNS which can be done in a docker container. Most people I know sailing the seven seas are quite adept at technology. Well most people I know are in IT in the first place so that likely doesn’t mean much.