Deactivating a bunch of Slack accounts is such a pain because of each having its own password. Is there even a benefit for doing this vs having one account to rule all of your workspaces, like Circle or Discord?

Yes, I didn't remember MOST of them because they were all different. And somehow the magic link isn't an option when resetting your password. So you have to reset password, reset password, use new password to login, and then tell them to deactivate.