The games are meant to be fast, so resistances would make matchups slower. Personally, I'd welcome them. Steel resisting psychic would make metal much more viable

i think weaknesses and resistances are by far the worst part of the pokemon tcg. having your deck take more damage and deal less because your opponents cards are a certain colour kinda sucks. you're not at a disadvantage because of low skill or bad deckbuilding, it just happens.