Yeah, Lucas even re-shot/re-edited the Darth Maul death scene as to split the character in two to make sure fans realised Maul was dead in TPM. I think I remember Lucas describing Maul as something along the lines of a being a henchman, a ‘pawn’, not a main villain etc… at the time when he was being criticised by fans for killing Maul off with little screen time in TPM - given the heavy marketing, PR, and merchandising of Maul as a character.
Of course it makes perfect sense that would bring Maul back to be the main villain in his Sequel Trilogy… 😉
So? Retcons have existed in Star Wars since TESB.
I think it makes more sense than introducing a random new villain whose just Palpatine again and then just bringing back Palpatine. That, plus, to me, the empty, irrelevant, black hole of a character that is Kylo Ren.