Not to say this is the holy grail of CGI, but just what is it that you expect? Considering we're dealing with a monster of sorts, I feel that some people give negative feedback on the CGI when in actuality, they're expecting something as real as you or me.
This reminds me of the jump to the current "next gen" consoles. The vast majority of gamesite reviewers kept mentioning how they envisioned a much bigger leap when the truth is that there was some great improvements between the three systems. It's just that they let their minds roam to some absurd change that perhaps was not practical at this time.
I'm not implying that you shouldnt have a big imagination or that one isnt entitled to expectations, but this is an animated monster. I'm pretty impressed with what they have done with that in consideration!