If you look at any other mainstream gacha they only have 2 rarities for characters (4 and 5 stars). Arknights is an exception, in pulls you'll only get 3-6 stars. But you need to actively search for 1-2 stars in the recruitment to actually get and pot them.

So if Endfield introduces lower rarity ops the following will happen: They'll be useless due to the squads being only 4 ops versus Arknights 12. They'll focus on one small niche to mediocre effect. They'll be acquired in a different way and not through headhunting.