Should I use a dedicated password manager instead of Firefox's built-in manager?

I store all of my passwords in firefox's built-in password manager. They auto-fill into websites, sync to my phone, notify me if one appears publicly, and I can generate strong new passwords conveniently. The pw vault is stored encrypted in the cloud as far as I know, but I don't really know the technical details. I presume that it's just as secure as using a "proper" manager.

Is there a problem with not using a dedicated password manager? I used to use LastPass but then.. I stopped. And at the time I didn't see anything wrong with just sticking with FF.

Using Firefox is fine right? If so, what's the benefit of something like BitWarden/etc over the built-in one?