I enjoyed it immensely, the CGI used for Tarkin and Leia didn't pull me out at all.
I do find it funny, that some fans are like the following;
Fans: "We want more Star Wars!"
Studio :"Okay,here"
Fans: "This isn't want we want!"
Studio: -_-
I think a more fair way to put it would be:
Fans: "We can't wait to see another good Star Wars movie that will wash away the bad taste of the prequels."
Studio: -Interference, reshoots, lots of fan service-
Fans: "Hang on, it still needs to hold up as a decent movie too. You can't just throw a bunch of X-wings and Tie-fighters at us, and expect we'll automatically like it. You need a good screenplay, a good story, good acting, and it needs to stand on its own."
You are aware that the AT-ST is in ESB, right? And doing considerably less....
That's where it made its first appearance, of course. As an extra background vehicle. It wasn't until Return of the Jedi that they decided to give these things their own action scene, and boy did they go all out. When the AT-ST shows up in Empire Strikes Back, it is part of a massive assault on the rebel base on Hoth, and its the AT-AT's that are the main focus, and the main threat.
So what was the focus in Rogue One? They have AT-A(C)T's in Rogue One, and they build a very long action scene around that. But with the AT-ST, they show it in the trailer, thus building up excitement... and then it turns out it's not really used at all. Why drop such an iconic vehicle in the movie, and not use it? The moment that thing shows up in the movie, you'd think that would be a big deal in an urban ground battle. And they certainly draw attention to it. It could turn the whole battle around.... but nope, I guess it's gone now. See, and that is why it bothered me. In an urban battle that thing would be a pretty big deal. In Empire it was but a minor detail among the much larger and more dangerous AT-AT's.
Besides, it wasn't iconic until after Return of the Jedi. They could have had some other new vehicle in the background, and I would not have been bothered by it quite as much. But when you drop such a well known vehicle in your urban action scene, and then not use it at all, it really sticks out. There was such a lack of focus in this movie!
And how many fans were excited for a big urban AT-ST battle after seeing the trailer? I bet a lot of fans were excited to see that. Why build up excitement for something, and then not have a pay off in the movie?
It's bad direction, bad screenwriting and bad action choreography.