I think the key difference is how the eyes are “reanimated” in the deepfakes. Rendering realistic eyes (with that trademark “spark of life”) has always been a challenge in real life emulating CGI, but now these new clips kind of capture the spark in the actors eyes much better. Luke Skywalker's eyes in the original clip kind of look dead plastic, the kind you’d find in real-time gameplay (not to mention this nose also looks like the product of bad rhinoplasty). The deepfake does this much better, in my opinion.

Elsewhere in this thread, someone posted a similar comparison clip about The Irishman and the difference is even more pronounced there. De Niro’s eyes actually look the age they’re supposed to be in that scene. The original scene had two key problems, in my option; one, they decided not to touch the eye and focused on smoothening the skin (I assume this is because of the technical limitations of doing the deaging in painstaking CGI); two, and this is a little more of a mystery, is that they thought they could get away with using De Niro’s current 80 year old voice on a character that is supposed to be 35 (ages are ballpark numbers). The raspy voice of an old man is just not something you expect out of a supposedly much younger and healthier man. They should have just gotten a voice actor who could do a convincing impression of De Niro in the 70s and dubbbed him in.