Normal people use Netflix (especially when DRM was first introduced) and watch YouTube.
The reason Mozilla can even still hold 10% market share in places like Germany is that they're much more compatible with the monopolist than you'd assume, given the circumstances.
Principled stances land you where the GNU operating system is. In obscurity, where people reference you as ethical, but with few actual users outside of versions that are ideologically watered down (but without your control).
I'd wager that stalling of GNU OS is as much due to inherent product engineering or design complexities as folks attribute to its principled stand. There are other operating systems like Debian, Mint and Fedora which work pragmatically on your laptops despite having a principled stance.
The "true" GNU Operating System is essentially every distro that's fully free software - to the point where you're excluding things needed for basic functionality like firmware blobs, with the proposed solution of "just use hardware that doesn't need that software". Only about half a dozen distros go the mile to get that stamp of approval, and most of them are forks.
You might think that Debian fits that criteria, but offering to enable the nonfree repo (and likely the nonfree repo itself existing) disqualifies it as an endorsed GNU system. That's the comparison.
They don't have a principled stance from a GNU point of view. Debian installation media includes non-free software [1]. The killer feature of Ubuntu and its derivatives was always built-in support for proprietary codecs and drivers that actual regular people aside from Richard Stallman expect to work.
Yeah, while I think Mozilla has made a lot of bad decisions over the years (looking at you, Pocket integration), supporting Netflix was not one of them.
Stubbornly clinging to principles at the expense of the user experience will alienate all but the most hardcore users.
The reason Mozilla can even still hold 10% market share in places like Germany is that they're much more compatible with the monopolist than you'd assume, given the circumstances.
Principled stances land you where the GNU operating system is. In obscurity, where people reference you as ethical, but with few actual users outside of versions that are ideologically watered down (but without your control).