If you really want to delete your account, you can do so from your Airtable account page. To access your Airtable account page, click the circular face icon in the top right corner of the homescreen. This will bring up a dropdown menu with several options; select the option "Account" (which has a little silhouette of a person next to it).
Toward the bottom of the "Your Account" page, there is a dialog that says "Need to delete your account?" with a trashcan next to it.
Clicking on this will bring you to a final screen—click the red button that says "Yes, confirm deletion of my account."
Please note that if any of your teams or databases are shared with other people, deleting your account will not delete those teams and databases. In order to delete those teams/databases, you must first remove all shared users from each of those teams/databases, and then delete your account.
Also note that if you are the sole owner of a team with multiple members, you will need to transfer ownership of that team to another member before deleting your account.