You can play it solo and go at your own pace. Just make sure to watch your back when exploring, and eat the right combination of foods for stamina/health. Co-op just makes it easier, but could also be more of a pain if you play with the wrong people.

Even though the game has multiplayer, ultimately, there aren't enough controls/options that allow tweaking of multiplayer worlds. Also, there is the thing with security and 'cheating', as well as some players going far ahead of others, making the world more difficult for newer players.

Also, another thing. Since the game is in Early Access (EA), the world's fog of war matters in the sense that any new major updates that introduce new world objects, will only appear in places that haven't been explored yet out of the 500 metre radius of sight. So playing solo, you can make it so you explore a bit slower outside of the spawn island and only take on the surrounding islands, until another major update. So on and so forth, if that makes any sense. ^_^