I wasn't serious about Carrie Fisher in the Last Jedi. I already knew it was filmed before she died.
As for my expectations of CGI - well, yes, I do want to not 'tell the difference'. Isn't that the whole point? If it isn't the point then surely the actor could simply stride on in a rubber Peter Cushing mask and we'd all be charmed by it. At least the lighting would be more of a piece with the rest of the shot. Why on earth would they be bothering with expensive CGI when a £5 mask would do? At the moment they have the skill of a conjurer who is telling us 'See me defy the laws of nature' but we can see all the sleight of hand and wires and mirrors. Almost there and certainly skillful - but not there yet.
I haven't seen a whole face done better - although I have seen better, if easier CGI face changes. For instance there are several of varying quality described here:
http://www.gamesradar.com/7-movie-actors-made-impossibly-young-by-cgi/ Orlando Bloom was probably the best, but then he looks like a CGI creation anyway.
There's a definite distinction here. When Ray Harryhausen's stop frame puppets career across the screen, we can see they're puppets. Yes he aimed for realism, but it was the best he could achieve. There were lots of bold claims about what we would believe and so on, but in truth the enjoyment is in spite of them being obviously animated puppets. Our present generation of CGI animators are saying we can actually produce something that looks real - as if Peter Cushing had really been there. What I object to is that if they're going to make that claim then it simply won't do to review the footage and say 'OK, his head changes shape but that's near enough' or 'in this section the CGI bobs about like Muffin the Mule on an actor's neck but Hey, it's pretty good'.