It is normal that people use the same teams over and over in Ranked PvP as you play to be at the top of the ladder, to get more rewards and be one of the best. It is also understandable since this is an MMO and people usually stick to one or two teams they always use to avoid having to farm another one, since PRO is obviously not as flexible as a simulator like Showdown. There is also no real incentive to play with weaker pokemon at all outside of you having fun and playing with your favourites. The active pvp playerbase is not enough for PRO to have additional lower tier ladders.