I just did a quick review of your EtreCheck report and two things stand out for me:
- Under the Performance section, your system SSD is showing a write speed of 402 MB/s. It should be closer to the same value as the read speed. This could potentially indicate an issue with the drive. To get a better look at the drive, I suggest that you get a hold of the DriveDx app. Run it and post its resultant report.
- You have a number of apps running on your Mac that are either crashing frequently or causing high CPU usage when they do run.
As you already know, identityservicesd plays a key role in iMessage, FaceTime, and Continuity features. It helps macOS identify who you are (Apple Account-related), verify that you’re logged in, and handle the secure communication and syncing of identity information across your devices.
If you're noticing high CPU usage or network activity tied to identityservicesd, it’s often related to an issue with your Apple Account login, corrupted keychain items, or sync conflicts. As you guessed, a good first step in troubleshooting is to log out of iCloud, restart the Mac, and then log back in.
Sometimes resetting the System Keychain can help ... but this not something that is recommended in macOS Sequoia as this keychain is under SIP control. However, if you know what you are doing, you can remove problematic items without resorting to nuking the keychain entirely.
Note: With Sequoia, Apple separated password management from Keychain Access to the Passwords app. However, Keychain Access still retains the role for system-level credentials, certificates, and cryptographic keys.
