I agree. Examples: they abandoned their Persona project. At a time where identity, sign-in, authentication and security are as important as ever, they've left the field wide open to privacy-invasive companies like Google and Facebook.
Rather than build an OS, why not create the foundation or platform for others to build on? I am thinking of Electron here. Although, I am not a fan of Electron, the framework and approach are gaining a lot of traction with developers. Where is the slim, fast, embeddable Firefox engine that's easier to deploy and develop than Electron (and superior to the heavy embedded Chrome)?
What about offline capabilities for web apps? Firefox should be trailblazing in this space. This is a huge privacy advantage (amongst other things) over cloud-based systems.
I really want to see Firefox succeed, but am worried they have lost direction and focus, or even the ability to excite and inspire developers with their future plans.