The concept of the Sith is a good idea but all the details that Lucas outlined about them should be ignored.

In ANH when Tarkin says “The Jedi are extinct, their fire has gone out of the universe. You, my friend, are all that’s left of their religion”. This implies that Vader is meant to be a “Dark Jedi” or a Jedi who uses the dark side of the force, so the word Sith shouldn’t be used in the PT.

Things like the Rule of Two were just made up as an explanation for why Vader and Palpatine were the only ones in the OT.

When Obi-Wan says to Vader “Only a master of evil Darth” this implies that this is the first part of his name and not a title that was given to him, so all other Sith/Dark Jedi shouldn’t have Darth in their names. Palpatine should just be known as Palpatine, Count Dooku should just be known as Count Dooku, and when the name Darth Vader comes up it shouldn’t be revealed that it’s referring to Anakin.