Sometimes, macOS partition went wrong which Disk Utility couldn't recover it. Most of time, it is not a hardware failure but software failure. My iMac had 2 Fusion Drive failures which let me delete all the things and recovered from Time Machine backup. It was a painful experience because it is Terminal related method which requires a lot of commands. During beta period, no one could help you. I think I will lose all yearlong asset. Luckily, I've found an easy method to recovery all the things.