Why was the CGI so bad in Episode 3? It was so overdone that it was embarrassing.

Also, in the throne room attack on Palpatine, the Jedi that were with Mace Windu were embarrassingly bad. He led 3 other Jedi with him. 2 were destroyed immediately because they decided to raise their lightsabers over their heads instead of assuming an attack position. How did they even come close to graduating Jedi school?

I would also appreciate Superkid's insight.