I think the Fortinbras bit -- the threatened invasion at the beginning, not just the arrival at the end -- makes the play about more than Hamlet's angst. The politics is why Ophelia is no match for Hamlet, as Laertes tells her. And it's occurred to me (just now) to wonder if the need for a better king than Hamlet Snr wasn't part of the grounds for the murder. A palace coup, nothing personal, in the face of external threat that the then leader just wasn't good enough to handle? After all, Hamlet's father is expiating great wrongs in Purgatory, and his advice isn't much use to Hamlet (or to the State of Denmark, come to that).