yeah that's my "point". the fans expect Vader to be portrayed a certain way, while the people making the actual movie chose differently. i'm not arguing that he did or didn't kill people, it's down to the way it is portrayed in the actual movies. not what "should have been". he is not an unstoppable mudering beast that makes everyone cower in fear (look at how Lando's city signed up in Empire). that is kind of a power fantasy people project on him.
when he is killing Jedi students, it is a sad thing, when he is killing Tuscan raiders, it is a sad thing. RO on the contrary was a glorification of killing. he's just slaughtering people, aimlessly, since as soon as ANH starts up, he's letting the troops do the work and coming in with "If this is a diplomatic ship" talk. he switches off his sudden mass murderer mode and is Good Cop all of a sudden.
the new guys just have a problem framing these things. they don't think it through, they just do what looks badass for the scene without any thought. so we are seeing that bite them in the ass right now. Kylo Ren introduced in the first film killing various villagers, then personally overseeing the genocide of an entire system. yeah it's "totally badass" but it also makes it so that when you try to redeem him, nobody is buying it. you look at all the first hand death Vader was involved in across the OT and it is actually very limited by comparison. Vader is shown killing mostly imperial members or Rebels directly involved in the war, whereas Kylo is shown killing civilians as well from the first scene.