That's not real DRM then. The real DRM is sending the content such that it flows down the protected media path (https://en.wikipedia.org/wiki/Protected_Media_Path) or equivalent. Userspace never sees decrypted plaintext content. The programmable part of the GPU never seen plaintext decrypted content. Applying some no-op blur filter would be pointless since anything doing the blur couldn't see the pixels. It's not something you can work around with clever CSS. To compromise it, you need to do an EoP into ordinarily non-programmable scanout of the GPU or find bad cryptography or a side channel that lets you get the private key that can decode the frames. Very hard.
Is this how YT works today? Not on every platform. Could it work this way? Definitely. The only thing stopping them is fear of breaking compatibility with a long tail of legacy devices.
the real pain in the butt in my present is Patreon because I can't be arsed to write something separate for it. as-is, I subscribe to people on Patreon and then never bother watching any of the exclusive content because it's too much work. some solutions like Ghost (providing an API for donor content access) get part of the way to a solution, but they are not themselves a video host, and I've never seen anyone use it.