Is this why Star Wars effects were deemed so crummy they were replaced by CGI? I.e. in ESB and Rotj were the effects composited in 65mm then copied to 35mm which is probably better?

All the Star Wars films used VistaVision for their elements. That was ILM’s thing during the entirety of their photochemical years. Boss Film used 65mm. And in all three films, the final VFX shots were squeezed onto Anamorphic 4-Perf stock in order to be cut into the negative reel with all the Non-VFX shots.

In terms of which is better, VistaVision or 65mm - Their quality is so high that that a direct comparison is almost inconsequential. It is like asking, which University is Better Princeton or Yale? Which tastes better a blood orange or a navel orange?

The only person who deemed the VFX shots in the original Star Wars as “crummy” is George Lucas. Because he imagined something larger.