Since I updated to the latest Xcode version 11.0 (11A420a) the debugging is extremely slow and cumbersome.
EDIT: After updating to 11.1 GM (11A1027
Have you tried running Xcode in safe mode? It's not ideal, but this was the only way I could get it to run efficiently. That is until the recent Catalina update where my device is no longer detected in safe mode. So I'm back to square one now.