Have you sailed around to all the land masses and explored every part of the map? Have you cleared all dungeons? Have you built in all biomes? Have you seen the biomes? How high are you skill levels? Are you a animal farmer/tamer/master (however you want to word it) yet? There is stuff to do, you just have to want to do it.

I think if you just want to fight bosses this is the wrong game for you.

Also, maybe try a server with people on it. There are people advertising all the time to join their servers. Maybe playing with people will spice it up for you. Turn on PVP ... see how DEAD it is then.