There’s a rather-pointlessly-trippy partly-animated film called The Congress about this (well, to the extent a self-indulgent psychedelic cartoon deepity can be about anything) that starts promisingly as actress Robin Wright sells her digital likeness, allowing “her” to appear in computer-generated films. As part of the deal, she has to retire from actually acting, as it may dilute her brand.
And after that interesting premise get brushed aside, the rest of the movie is akin to being bludgeoned with the LSD-saturated skeleton of Philip K. Dick.
I prefer real actors 99% of the time, but I have enjoyed the de-aging and recreation of actors for the sake of continuity that have happened.
Entirely photoreal imaginary humans seems an unnecessary complication, and would ultimately be distracting for me. The most famous attempt at that was probably the Final Fantasy Spirits Within from 20 years ago. Subsequently that technique has been used very well in video games.
But movies and TV is going too far, and knowing that it’s being done for no logical reason would be forefront in my judgement.
They did an amazing job with the “Young Will Smith” in… whatever that movie was (guess it was pretty forgettable; the one where the real Will is fighting a younger clone of himself).
But even at that, I was constantly taken out of the movie to think "Why couldn’t they just get a young actor that looks enough like Will Smith and put some makeup on him? His mannerisms are so broad and unique, I bet a dozen kids could play Young Will.
Oh, there were a couple of instances of Rag Doll Physics there, too. It baffled me that some of it was even in the trailer. So going in, I’d already seen CGI Will fall off a motorcycle and get tossed into a car… and I never for a moment thought it would hurt “him”. I could tell that the CGI character had no mass.
If you couldn’t tell them apart, sure, use computers. They’re cheaper in this scenario anyway.
In the real world, computers will never be as good as human actors at acting like humans. So Johnny Depp doesn’t have to worry about the robots coming for his $20 million paycheck.