Okay, it irritates me that Safari has quit supporting ad blockers that don't use its Content Blocking API, an extremely limited API that can only do URL-based blocking. It doesn't permit blocking pre-roll ads on YouTube, for example, making it unacceptable to me. Safari always ran kind of slow with blockers installed, so I can see why they did it. On the other hand, why the fuck is it so slow with 3rd party content blockers in the first place...