Regarding Vader and the negative portrayal of prosthetics/cybernetics, I think this is more like a visual metaphor for losing one’s humanity. In a separate conversation I was having in the OT section with ZkinandBonez, we were talking about how Star Wars is to some extent written as a timeless piece of mythology. If it weren’t set in some psuedo-futuristic space civilization, but instead set in like, a Lord of the Rings type high-fantasy environment, Vader would be something like a “Ring Wraith” or Gollum or some kind of decrepid yet powerful being, whose loss of humanity and descent into evil is symbolized by some kind of physical deterioration or dependency on dark magic. Vader’s cybernetic suit and iron lung serve a similar function, as a visual representation of a formerly good person who became evil. The cybernetics was simply a handy visual metaphor suggested by the sci-fi setting.
There’s also buried underneath all of this a very Christian theme of a “deal with the Devil” type thing, where achieving great powers of darkness comes with a very severe price of physical deterioration. Lucas implemented this idea very literally with having Vader fall into lava after embracing the Dark Side. The Emperor also appears physically deformed, presumably because he’s been screwing around with Dark Side powers for so long.
However, I don’t completely agree with this interpretation. I think it’s partially true, but Vader’s cybernetic suit also serves as a manifestation of a very modern fear about technology consuming our humanity (whatever that means in practice). This is a running theme in Star Wars, where reliance (or over-reliance) on technology is considered a bad thing, which is why Luke has to switch off his X-Wing targeting computer before pulling off the impossible shot, and a primitive Ewok tribe is able to defeat the technologically advanced Imperial troops.
Regardless, the idea that the cybernetics somehow makes Vader less powerful is really an entirely off-screen idea that isn’t really apparent in any of the films themselves. If I recall correctly, the first time I even heard this idea was in the context of trying to reconcile the highly kinetic, acrobatic, fast-paced lightsaber duels in the Prequels, with Vader’s slow, sometimes almost clumsy fighting style in the OT. In other words, the idea that cybernetics makes Vader less powerful probably emerged from out-of-Universe inconsistencies in choreography and special effects between the two Trilogies.
I always thought this was obvious and it’s very bizarre to me when people talk about the dark side like it’s just getting emotional or choosing the wrong politics. Which means if you like those emotions or those politics it’s a legitimate choice.
It literally turns you into an inhuman cyborg or a freakish monster with gray skin and yellow eyes. It’s supernatural. It affects Force users like an addictive drug. It isn’t just getting afraid or mad sometimes, it’s having hatred in your heart and a lust for power.
Note that Vader didn’t just replace his limbs like OG Anakin or get a normal life support system. He’s in an armored suit designed to frighten and intimidate people so he can lead the evil empire from the front.