The Han Solo movie is an entire film set years before ANH. They had to recast. The cgi option would have caused the budget to increase substantially. Plus they would have had to create a model of Han Solo's head that looks even younger than Harrison was when he played Han in ANH. The whole thing would have just been impractical to do for an entire film set years before ANH.
With this Leia scene however it is a single scene, and takes place at the same time as ANH so they don't have to deage Fisher's face any. They just had to render a cgi model of Fisher's face as it was in ANH and use it for a single scene. And considering it looks pretty good imo I think it's preferable to a recast. It would have been weird for Leia to be played by a look alike in the final scene of Rogue One and then in her next scene (her first appearance in ANH that takes place moments after her scene in Rogue One) be played by Fisher. I could have put up with a recast, and until I saw cgi Leia considered recasting the better smarter option, but I think they pulled it off well enough to justify going with the cgi option.
That being said, I understand that it's not everyone's cup of tea, and I'm sure there won't be many fans that approve of this approach. I really thought I wouldn't like it or be ok with it because of the reactions I had read, but having seen it and considering the amount of time it's on screen I'm ok with it.