This is random but rock is such a flop type. It has a million weaknesses and all the good rock moves can be learned/taugh to like every other type. They're only good for rock smash tbh.
Kings Aerodactly, Cradily, Tyranitar, and Aggron beg to differ! Pretty much all the fossils, actually except the Gen 6 dinos
Rock is probably the most important type! If you're weak to it then you're automatically knocked down a bit and if 4x weak then you're practically unusable!