A lot of systems are gated behind your Adventure Rank so as not to overwhelm new players with the surprising number of different systems like daily quests, dungeons, world bosses, and more.
In Genshin Impact, Adventure Rank determines your overall progress through the game and increases bit by bit every time you do anything, from completing quests to simply opening hidden chests. You have to first level up your Adventure Rank to 16. The first problem players will run into is that co-op isn't unlocked until way further into the story campaign than it should be. It's a shame that Genshin Impact is structured this way, especially because things like sharing loot and completing quests aren't a problem in other games. If you have got a few friends who are interested and hoped you could all experience the game together, I've got some bad news.
In the 35 hours I've played over the past few weeks, I've only played co-op a handful of times, and I don't think I'll spend any more time with it. But Genshin Impact's co-op is too restrictive to really be of much use. Playing with friends in a big open world RPG is so enticing people have spent years modding games like Skyrim just to make that dream a reality.
