Are you exploring much? The level design in FO4 is so good, even better than FO3. They're using vertical space (roofs, etc), many locations are very big inside and go on and on and change from one thing to another (Andrew Station), some are just interesting for the detail (Kendall Hospital), some have interesting things going on (Dunwich Borers, Fens Street Sewers, HalluciGen, Cambridge Polymer Labs ), some have great combat (Gunner's Plaza, Saugus Ironworks), there's a lot going on with the overpasses (some have elevators and camps) you can walk a long way on them. Some locations may trigger epic battles between factions (Big John's Salvage, Wilson Atomatoys Factory), Quincy Ruins has two bosses, good use of vertical space and many Gunners, if you haven't been to the Milton Parking Garage you should go through that, the middle school in Malden is worthwhile. There's just so much content in this game; maybe not as many quests as we'd like, but so much to explore.
Oh, and If you haven't found/been given the marker for the Pickman Gallery it's definitely worth seeing/doing/getting the reward.