I cannot delete reminder list

iCloud: Add and delete reminder lists on iCloud.com

All reminders you create using Reminders on iCloud.com are put into a reminder list. iCloud Reminders comes with one list for active reminders, and a list for completed items. These lists can’t be renamed or deleted, but you can create additional reminder lists. Organizing reminders into lists makes it easy to keep your work, personal, and other to-do items separate from each other.

Create a new list

1. Click the Add button  at the top of the window, above the reminder lists.
2. Type a name for the reminder list in the text field that appears, then press Return.

Delete a list

1. Select the reminder list you want to delete.
2. WARNING: When you delete a reminder list, the list is deleted on every device where you turned on iCloud Reminders. All the reminders it contains are also deleted.
3. Press the Delete or Backspace key.

Note: If you accidentally delete reminder lists, you can use iCloud.com to restore them. For instructions, see Restore contacts, calendars, and more in iCloud Settings.

iCloud: Add and delete reminder lists on iCloud.com - Apple Support

https://support.apple.com/kb/PH12087