After an extensive search and many non-working solutions...
I've had the same problem for months. Have to hold down the power button to make the computer shutdown on its own.
The fix is a surprising one...
Device Manager -> Universal Serial Bus Controllers
Go down the list and any of them that has a "Power Management" tab, uncheck "Allow the computer to turn off this device to save power".
At least this worked for me. Apparently its the USB controllers preventing the proper shutdown for some reason.
Perfect solution, even today, October, 25 2024.