Counter-examples: Privacy (almost always getting worse), security (no clear trend, but it would be hard to argue it's consistently getting better), usability / discoverable interfaces (debatable)

Privacy, I'll agree with.

I think security is getting better but what we see now are the consequences of years of poor decisions. It's the post-Christmas credit card bill.

This is rather debatable when it comes to human-machine interfaces. UI goes through phases of improvement followed by radical degredation due misguided, cargo-culted redesigns. Take cars as an example. In my car I can adjust the airflow and temperature with a button and a knob, but in newer models a touchscreen or voice command is required that takes quite a bit longer.

Mozilla as an org is off the tracks and has been for a long time.