> can also be levelled at the others
Password manager storage/exchange formats? Sure, there are no standards at this point. Arbitrary formats or protocols? Certainly not. Similar cannot be said about e.g. HTML/CSS or WebDAV or OpenPGP - even though there are enough incompatibilities, deviations and proprietary extensions.
> The only way mozilla could not have caused that problem is to not have built anything like this.
Of course. I don't think anyone needs yet another password manager, for there are a lot of options already (although many lacking one thing or another, but it's not like Lockbox is going to be the perfect one).
Mozilla are in touch with standard bodies, like W3C. They are participating in development various authentication protocols like FIDO2. Surely they can raise a call for other password management software vendors to devise a common API. Some would not want one (besides importing into their product), some would enjoy a capability to concentrate on some parts of the product but leave others to compatible third-party implementations (e.g. backend/frontend separation).
It's not a bad thing, of course, to build another password manager. I just don't see anything good about this, either.