I'm finding the same thing. On an iPhone 14 Pro, 2000 annotations is unusable even if none of them are on display. Unless I'm missing something, it's regenerating all of the annotations every time the user interacts with the map. (A MapKit version of my map handles 6000+ without getting unusably laggy even when it's fully zoomed out.)
For clustering, you might want to look at https://github.com/vospennikov/ClusterMap.
Topic:
App & System Services
SubTopic:
Core OS
Tags: