And that's why I think they went with prosthetics instead. Just because something looks unconvincing doesn't prove it's CGI. Prosthetics have decades more history of being unconvincing than CGI does.
Digital retouching is routine in any number of contexts. That doesn't prove they didn't use prosthetics as well. For instance, they could've retouched his hairline to disguise a seam in the makeup. Prosthetic appliances like masks and bald caps have never worked well with foreheads; that's where you're most likely to see the seam or wrinkles in the latex as the actor's brow muscles move underneath. So they could've used a mask and then digitally erased the evidence of the seams or wrinkles afterward, like how
Avengers: Endgame put Chris Hemsworth in a full-body prosthetic for his out-of-shape appearance and digitally erased the seam on the back and the occasional wrinkles that showed up as he moved.
Anyway, we're both just guessing based on what we see. The only thing that would really answer the question is actual comments from the show's producers or actors about how they did it, and I can't find anything to that effect online. The closest thing I can find is this statement from Spiner:
https://trekmovie.com/2019/08/01/st...-clue-about-datas-return-in-star-trek-picard/
That sounds to me like it's saying he was in makeup for
Picard, although it's ambiguous, since he was talking earlier about the time it took to get into the makeup back in TNG. And it could be that they applied a basic Data makeup to his aged face and then digitally erased the wrinkles. But I have a hard time believing that would look so much like they stuck prosthetics to his aged face to cover the wrinkles. That's the only explanation I can think of for how puffy and rubbery his face looks. If it were digital, I'd think they could tweak the shape of his face to look more like it did in the past.