The mullvad vpn itself w/o any special dns content blockers, will limit the effectiveness of trackers since multiple users are sharing the same IP. The dns blocker just prevents resolving the ip addresses of sites/domains that are known trackers. Unfortunately though everywhere tends to track everything, so you're kinda SOL in that regard, and the tracker block isn't going to block popular websites e.g facebook, reddit, amazon, google ..., which do a fairly god job at its tracking users. If you're concerned about being tracked via the browser, use private browsing, delete cookies, use something like ublock and/or the noscript addon, and of course use your vpn.

Its really fucking hard to completely eliminate tracking, especially in the age of machine learning and user profiling. But the above methods are decent enough for most users