Currently the only NPC you can interact with is the trader. The devs have been leaking some info that a new NPC is on the way, though there isn't much info besides it being called "Hildir's Quest". The update involving all of that could also be many months away.

The game is fine solo, but having friends can make it more fun and purposeful. Otherwise, it will end up as you said:

Originally posted by robtock216:

...you just wake up one day and realise your just 1 dude knocking around a massive city you somehow built solo, doing all the menial jobs like smithing, smelting, collecting wood and mining all on your own, for no apparent reason.