Cannot manage account without installing the extension.
Cannot delete a pre-existing account without paying for a plan.

Edit: After talking to support, you CAN delete your account without a plan. But, you need to go directly to the account deletion page (I would link, but cannot include links in add-on reviews). Also, you must have the extension installed to access the account deletion page, you do not need to be logged in, just have the extension installed.

It's reeeeally useful add-on

Used for 10 yrs or so. Never a problem.

Worst updates ever