It's not a direct attack, and theoretically what you said is true. However practically it won't be. The "networking effect" will come into motion.

Look at it from consumer perspective. They can choose a web browser that supports their favorite service, for which they have subscription or use another open source and free browser that doesn't support their favorite service. People leave, which leads to reduced revenue for that browsers and its development stalls and slows, leading to further loss of interest and eventually its death and/or fading into obscurity.

So open source and free browser, won't have much freedom other than to apply it however silly that sounds. So its not so much an attack on consumer freedom, but an attack on browser vendor's freedom.

This if ofc moot if OSS browsers can introduce DRM into their core, which might be possible.