Completely disagree. Using the Firefox master password feature passwords are safe even in the context of sharing a device or an extension. In addition, multi-FA isn't necessarily a safer option.
And what's the provided alternative? A password manager. So storing passwords somewhere else that may leak, and in fact has leaked, and is by its nature a high value target.
Each person has to consider their particular situation and threat model, but a well-secured browser that stores passwords locally can be a perfectly adequate and in fact safer alternative than a password manager.