Ottawa is a small city (under 1 million people), and the main business in the town is politics. It is the capital of Canada, and it is populated by lawyers, accountants, senators, data research analysts, political party organizers, and other not so exciting professions.
That's not to say that the people there are not fun, are not wonderful people, or that there is not things to do in Ottawa. But the issue is that much of the businesses cater to "government" operations and it's not the most exciting place. Why do you think so many young Ottawa residents head to Gatineau for excitement?
As you pointed out, once you get past the Parliament buildings, and the various museums, there's not a lot else to do. There is hockey in nearby Kanata, and the Roughrider stadium (do they still call it that?) has concerts and will soon have CFL football again.
But what is it that you like to do? I am pretty sure you can find something to do this time of year. An arcade? Skating on the Rideau? Laserquest? Indoor paintball? Movies? Hang out at the mall?