That's not entirely true. Tyranitar's combination of bulk, typing, and power allows it to check prominent threats such as Latios, Mega Charizard Y, Gengar, and Talonflame. In addition to this, its access to Sand Stream and Stealth Rock makes it a great support threat, as it assists Sand Rush Excadrill and Sand Force Mega Garchomp. Sand Stream itself boosts Tyranitar's Special Defense, meaning it can tank Latios's Draco Meteor with ease. Its great movepool allows it to lure in common switch-ins such as Mega Scizor and Landorus-T and KO them with a coverage move. Tyranitar can also take a role of a sweeper through its Mega Evolution, making it an unpredictable threat. All in all, Mega Tyranitar is quite useful on various occasions