That is definitely a much more impressive demo than the Rogue One attempt from 2018. There were a couple times I actually said “oh wow” out loud 😃

But I think the difference is that the facial de-aging in The Irishman is (correct me if I’m wrong) begun with filmed capture of their actual on-set performances. So this video shows the VFX artist deepfaking faces on top of camera-captured real faces (albeit CGI-enhanced/de-aged ones), not full blown cgi-created facial movements. That could be why the mouths appear to move much more naturally in these deepfakes, because the mouths are actually moving naturally. If they were trying to layer a deepfake head over the top of a computer animated person, I’d bet the mouth movements would still look unnnatural because they’re trying to map legitimate human expressions captured by a camera to a fundamentally unnatural animated movement.

But I do think you’re right that what’s really preventing it from looking the way it was obviously intended to look by ILM is just time. In the space of a year deepfakes have gotten scary good, even moreso than they were when people first started getting scared by how good they were. Maybe in another year or two someone will know exactly how to deepfake Carrie Fisher into that footage flawlessly. Right now, I don’t think anyone’s there just yet. But it’ll probably happen, given enough time.

(although, considering how poorly her posthumous footage was used in Rise of Skywalker, and how not-good this Rogue One footage was, maybe everyone should take a whole lot of that time off from digitally de-aging and/or resurrecting Carrie Fisher, just on general principle)