Assassin's Creed Brotherhood: there's too much to do!

I've no idea why I started playing this, other than just fancying some climbing and sneaking action.  For someone who hasn't played previous games in the series, it must have been horrible, with hundreds of game mechanics introduced in the first ten minutes.  For me, who's completed the previous two games and rounded up most of the collectibles, it was bad enough - I could ignore the movement instructions but had to learn the new building upgrading mechanisms, Borgia towers, tunnel system, and then over the next hour or so learn about recruiting assassins and sending them to do jobs around Europe, opening up buildings for the thieves, mercenaries or courtesans, and finding bits of aqueduct that had fallen down.

All of which seems pretty superfluous to the main story, and means I make little progress.  I've just finished sequence 5, after many hours of playing, and the lack of urgency isn't doing the game any favours.  I am more interested in finding the viewpoints and liberating the city from Borgia influence than I am following the plot - all I know is that the people I didn't kill at the end of ACII still aren't dead and people still want them to kick the bucket.  Oh, and the glowing ball has been stolen again.

It's a quality production, and the city of Rome has been well modelled (although it feels a little small compared to the multiple locations of previous games).  I think soon I will run out of stuff to do in the areas that have been unlocked, and I'll be forced to continue with the story to open these out.