I'm going to have to take issue with the idea that the LotR trilogy used as much cgi as the prequels. They really didn't. Maybe a similar amount to what was in episode I, but that's because it still used actual sets, models, and other practical effects techniques in places it made sense. In the other two though, there was almost nothing. Even places where real sets would have been easier and made more sense, they green screened it all. LotR on the otherness had tons of practical effects and sets and it was fear that any scene was entirely cgi. It also had integration with the cgi and physical stuff that was stupidly good,probably because they didn't blow the entire animation budget on the entire movie. Gollum still looks stupidly good and quite seamless. Far better than anything in the prequels, or even the Hobbit trilogy to be honest.

It really just does not compare. The cgi in the prequels is so bad it makes ILM look like hobbyists.