Former backblaze customer here, the trick is that you can't copy and paste your password as one might do with a password manager. You have to type it manually so that the web page can interactively tell you how strong the password is getting as you type it.

Backblaze lost me as a customer due to the new password and 2FA requirements, which would lock me out if I were to lose my devices, the exact scenario I'm trying to mitigate. Not affiliated, I'm now trying my luck with pixeldrain, mega, and koofr (having quit proton lately as well since it broke rclone compatibility a few weeks ago).