After the start, its basically imperative to be a part of an alliance otherwise you are always open to attacks from opportunists. As a result of joining alliances, independence is stripped away from you as a nation and you are essentially relegated to the position of a local government official instead of the leader of a nation.You get taxed, your cities sometimes have to be a certain way, everyone in an alliance is out of bounds in case of major retaliation that your alliance does not want to face. You cant really make deals or ally with other people too much because their alliances do not want to implicated in a war or whatever.
Every major alliance has treaties with other alliances which means we are all interconnected and there's nothing to do except wait for someone to attack you and log in once a day to check the status.
We dont have any extra features to play with like colonisation of the Moon or Mars. After buying the NPs, just twiddle your thumbs really.