The majority of the game is solo so you can do it at your own pace. However like Left 4 Dead for example MMOs become a lot more fun when playing with other people, whether that's simply just chatting in the LinkShell or doing Guildhests and Dungeons together or even just running around in an XP Party or even more (as is the case right now) just running around and exploring.

Alot of the social interaction also comes from striking deals with other players... ie you might be levelling your Armorsmithing but don't want to do Mining right now so you have a chat with a miner in the LS and make some sort of arrangement like "hey if you help me out with materials I'll make you some armor etc."

Higher end content like Raids etc can only be done with a group of people.

But for the most part you can do most of it without talking to anyone, the duty finder also allows you to do the group content that way. This is fine too, some people only play for the Lore etc and not being able to get a group when you really need one can be really frustrating so the bulk of it is solo so you can do it at your leisure.

But any MMO becomes way more fun when you do stuff in a group.