AC:Brotherhood just became the next in a handful from my Steam Library to be dropped and uninstalled due to being just too bloated.
It seems to me that Ubi literally copy and pasted the formula for AC2, and instead of embellishing the Storyline from the main Campaign, just added as much additional meaningless waste of time chores as possible, instead of staying focused on the point of the series to date.
Given knowledge of at least 3 more entries in the series (including AC4), it is time to step back, say "no thanks", and make better use of my gaming time.
AC2 is the best in the series IMO so Brotherhood was always going to be a step down, also bear in mind Brotherhood/Revelations were supposed to be kinda spinoffs from AC2 (hence not labelled AC3/AC4) so it is understandable that they are similar.
One area Brotherhood did improve on IMO was the lairs, in AC2 they are quite unforgiving i.e. basically long platforming sections where if you make a mistake you often had to redo a fair amount. Whereas Brotherhood mixes it up more with chases, platforming etc.
As for whether you should ditch the series personally if you can't hack AC:B then I would, as it is probably the 2nd or 3rd best in the series of 5 released so far.