If rolled out widely, this would make web browsers and third-party YouTube clients without a DRM license unusable for YouTube playback, download, etc. This would include almost all open-source web browsers and almost all third-party YouTube clients. Archive link to reddit post about this
I’m not making it out to be trivial, but I am realistic about the matter.
You can have in-stream ads to make things ‘unblockable’, but only so long as there’s no other side effects. Any side effects can be detected, that’s really just the reality of the matter.