They should have leaned into Kylo Ren worshiping Vader or some kind of cult centered around Vader imitating him. Then either Luke or Anakin’s ghost or both try to convince them that the real Vader was a slave to the dark side and not someone to be imitated or admired but pitied.
Likewise the First Order if anything should have been more of a cargo cult of the Empire or terrorists inspired by the Empire, not more technologically advanced than the Empire.