It’s probably for the best that Lynch didn’t do ROTJ. I can’t imagine Lucas would’ve give him any more creative freedom than he gave Marquand. Lynch’s ROTJ would’ve likely been as tepid a film as the ROTJ we got, only with some minor casting/aesthetic differences.
I kind of wish Cronenberg directed ROTJ, if only for a bit of body horror. Imagine a partially-skeletal Emperor, a distorted Jabba, or a less humanoid Vader.