The reason Fett was cool to kids in the 80’s was because he said basically nothing, was a bounty hunter, had - basically - a space version of Clint Eastwood’s dollar trilogy outfit mashed together with Spartan armor, and most importantly, you knew nothing about him at all at the time so you could imagine just about anything you wanted to.
He was the Star Wars ‘man with no name’ archetype…which was always a popular archetype for boys up through to at least the 80’s (obsession with character driven psychoanalyst narratives from the 90’s on started to take that away - you could have one, but you needed to learn more about them as the story went…kind of like The Mandalorean now).
Logically, he’s pretty “meh” if you stop and look at what we really see him do, but that’s par for the course of Star Wars.
Luke is…um…well…something. I mean Zorro even makes Luke look like amateur hour.
And as cool as Vader looks and as ominous as the camera and music plays him up, he’s jack all compared to any common SS soldier in WW2, or (sticking with fiction) Norman Bates from Psycho.
He’s more Dracula from the old movies. Implied evil more than much shown evil…most monsters and things like Dracula were pretty…well…lame by comparison to even a whiny nutter character like Joffrey Baratheon.