Afaict, it sounds like you won't be able to recover any of the system files if you really did wipe them.
If it is possible, I can't help.
And if there no system installed on the phone, I don't think you'll be able to use adb commands.
However, you can use fastboot commands to identify and flash a new ROM to the phone.
Code:
fastboot devices
fastboot flash zip WHATEVER_ROM_FILE.zip
But I can point you to a ROM that will work on your phone, assuming the boot loader is unlocked and you've installed the TWRP recovery by TeamWin.
To flash the new rom, boot into the recovery (hold the power button + the volume down button), then connect the phone to the computer, transfer over the WHATEVER_ROM_FILE.zip, then use TWRP's "Install" menu to flash the zip file. Or you may just use the `fastboot flash zip` command to push the zip to the device and install it as it's in recovery mode.
I don't have any links to the original stock ROM, but here's a good Nexus5X ROM (LineageOS 17.1):
Note that anything with "blod" in its name is for the battery loop of death. You really only need to flash those ROMs if you're device got into one of those boot loops.
Good luck!