ELO is a system that carries over from chess, and in that game it’s a very good metric for judging how well a player performs in competitive play. It works mostly because chess is an incredibly balanced game: both players have an equal numbers of pawns and pieces, the starting positions are identical, and in a match both players play both colors (this is done because white has the advantage of going first).
In contrast, Wild Beyond is a game where matches are inherently unbalanced: the players don’t have identical decks, luck of the draw is a function, unit and barricade levels add further asymmetry, and the card Madness exists. Considering these traits of the game, it makes little sense that an ELO based system should be in place. Have you considered altering the way rank works? Or maybe worked to reduce the asymmetry in matchups?