Alola: Too many Mono Types?

But to me making some Pokémon, like Lurantis mono seems like a waste. IMO, Lurantis should have been Grass/Fairy or Bug/Fairy.

Plus the few that ARE dual typed seem so random, like Minior really should have been Rock/Ghost. I swear GF are allergic to typing Poison, Ghost, Normal and Rock Types together. The only time we got any of those together was in Gen 1.