I don’t see how the “finding the secret to prevent death” is nonsense considering mortality is a big theme to the films. Force ghosts? “I’ve become more powerful then you can possibly imagine?”. Luke saying to Yoda that he can’t die and Yoda responding that that is the way of things?

As Lucas said, the epitome of greed is the desire to cheat death. The Sith are defined by being greedy and selfish. There’s nothing more greedy then wanting to take away a fundamental aspect of the nature of living things because you can’t accept the natural course of life. Therefore, it makes sense that the ultimate goal of the Sith is immortality. Having Anakin’s turn be about cheating death creates a nice retroactive arc when Vader accepts his death in ROTJ (“Nothing can stop that now”).

It’s an inherently fantastical concept, but this is Star Wars. The Force and lightsabers and stuff. Star Wars has mythological architypes all over the place, and mortality is a huge theme in all mythology. It was literally created to be a modern myth.

I do like the idea of Anakin becoming addicted to using his own anger in combat though, as well as wanting to control the galaxy using the dark side as he sees it’s more effective. That should be a part of his arc.

Also, in my opinion, I hate the idea of pinning the blame on the Jedi. Darth Vader should be a villain with agency who made his own choices. Palpatine should contribute and manipulate him, but it should ultimately be because of his choices. One of the reasons Walter White is so compelling is because he made his own choices. If it was just “Poor Walt, he has no choice but to cook meth, he just needs to provide for his family”, he’d become a weak and pathetic villain. Don’t strip Darth Vader of all his power by just pinning the blame on everyone around him.