They "caved" because it's a browser for humans and lots of humans stream TV. I don't miss the daily "how can I watch Netflix on Ubuntu?" posts in different communities. Users can disable Widevine in FF.
https://news.ycombinator.com/item?id=44294402
So they use Firefox 99% of the time and then if they encounter the rare thing that requires DRM they treat it like toxic waste that has to run in an isolated sandbox, which doesn't need to be the same browser they use for anything else.
The only other sensible option is to get out the reversing toolkit and break the DRM.