Well Lucas did not replace Tippett's stuff with cgi did he?
The Walkers are still the same. The Rancor is the same only recomped, the tauntaun has not been changed as far as i am aware not even on the blu ray.
Muren thought the Walker sequence in empire should have been completely redone in cgi and Lucas said it was not necessary, it was Lucas who saved the original scenes from being violated by cgi.