What people who are bad at Pokémon don't get is that having checks/counters alone does not mean a Pokémon is not overpowered or overcentralizing. The sheer threat of a Pokémon like Muhhazards-D means that you are forced to make certain moves. If you have something that can 2HKO or even 1HKO Muhhazards-D, you are essentially forced to play it, because predicting that your opponent won't is too much of a gamble. This means that all the prediction power is in the hands of whoever has Muhhazards-D. When two good players are playing against each other, and only one of them has an overpowered Pokémon, this Pokémon can decide the game even if it is not switched in a single time. This is what happened plentifully with the likes of Landorus/Keldeo/Tyranitar in BW days. You couldn't send out anything that could wall Landorus/Keldeo do to Tyranitar's presence.