Why? They allowed proprietary extensions (e.g. Flash) from the start. I don't like it, but I don't see how it represents a loss of their way. Mozilla was never GNU.

Big difference between an extension and being integrated into the browser. It's directly analogous to the difference between your OS being closed source and your OS being able to run closed source programs. The former is a liability; the latter is an ability that you grant to users to use the system the way they want.

The CDM modules are not integrated with the browser. The browser only has an (open source) sandbox to run them.

I don't like EME either, but not implementing it would've killed any chance of regaining users: "Oh look, Firefox Quantum looks awesome, I should try it. ... Never mind, it doesn't play Netflix". Implemeting it, but disabling it by default was a good choice. People will have to consciously click "I accept DRM" to use it, which might get them to read more about what it is and ultimately raise awareness about how terrible it is.

Yea, but they lost me today. EME annoyed me, and I took note of it, but I didn't leave over it. But now I feel like Looking Glass is the straw that broke the camel's back.

The world doesn't need another browser that sacrifices principles for market share. Chrome, IE, and Safari are perfectly good browsers for that. What I wanted was a browser (and software in general) that promotes security, privacy, open standards, and open source. You can accuse me of misinterpreting the situation, but that's what I thought Firefox was 10 years ago. It's not what Firefox is today. It's turned into just another organization that's optimizing for the continuation of the organization over it's own founding principles.