That's true, even if you switch DNS, they can still see the destination IP of every connection you make. That still means they can't see individual search terms though.
they can't see search terms with HTTPS
I think disabling third-party cookies helps a lot. If each site can only see its own cookies, it's harder to coordinate. Also, browsers have started experimenting with separate cookie jars for each top-level domain. https://techcrunch.com/2021/02/24/mozilla-beefs-up-anti-cros...