Instead of making password management modular, so any password manager capable of certain queries and operations (KeePass, LastPass, Bitwarden, KWallet/Gnome Keyring/libsecret, Microsoft Credentials Management API, Apple Keychain, etc) could become a storage backend with some programming effort... they're doing the exact opposite - they've created yet another password manager UI and yet another proprietary data format (Lockbox Data Storage) for that purpose.
Seriously, I doubt many (if anyone) but Mozilla management needs or wants a Mozilla-branded extra ecosystem, in addition to Google, Apple and Microsoft-branded ones - yet another piece of software that doesn't interoperate with anything but its own unique data formats and protocols.
I don't know what others want, but I want a good browser that I can hook up with things I already use.