My primary problem with Pi-hole or any other DNS-based blocker is that it silently breaks things. YouTube stopped saving my spot in videos. I couldn't click through on any link that involved a tracking service.
These things accomplish their stated task well, but leave behind an insidious trail of browser errors, broken pages, and broken apps without ever indicating to the user what the cause of the problem really is.
DNS just isn't the right tool for fixing shitty UX in the browser DOM or a mobile app. It's a happy coincidence that it works more often than not.