After Microsoft switched to Chromium as its code base for Edge, I left Firefox in the dust. The organization turned unnecessarily political and ideological, and as various security and privacy concerns were raised, I decided it was no longer worth my time.
To date, Firefox continues to store passwords in an insecure fashion: if someone has access to your logged-in session (like someone using your computer at work or school), they can easily access your passwords.
All Chromium-based browsers, including Edge, make use of the operating system's secure password storage - this is called Credential Manager in Windows and the Keychain in MacOS. Revealing passwords requires the logged-in user's password.
I strongly advise against continuing to use Firefox in any capacity. It isn't secure and will not keep your online account passwords secure.
Very old builds of Firefox still have some utility on older operating systems. Very old versions of Firefox classic are solid enough to use as daily drivers in Windows 9x and XP. I will be maintaining a mirror of themes and extensions I use, because there is no longer any central repository online where these may be found and downloaded.