i dont know if youve ever seen competitive 6v6 played at the highest level, but as a spectator sport its much much worse. The matches are longer on pokemon showdown which has no battle animations then they are for doubles on cartridge with battle animations. 6v6 also devolves into a certain subset of pokemon without community enforced ban rules, which the pokemon company refuses to do. If the competititve scene was 6v6 offical, I can assure you we'd have the exact same team diversity except even worse. Fluttermane is banned in ou for a reason

Edit: that being said, i think pokemon in general is a terrible spectator sport right now, because the stupid animations take entirely too long to process, e..g. having to watch each individual pokemon get hit by sandstorm, which is even worse in 4v4