I guess you didn't realize you were renting a decent movie based on an amazing graphic novel that is in many ways cynical and damning of superhero's and fluffy action moveis - because that's what this story is about.
The movie essentially tries to do what Jackson did with LOTR - take the big action beats that last like two pages in the source and expand them for thrills, while retaining enough of the narrative to remain intelligent. I think the movie failed a little at this, particularly the ending (which was changed in certain key ways) lost key themes and resolutions IMHO.
But in the end, I don't want to knock you, but from your points it simply sounds like you're juding the movie vs expectations you had on a basic level that were invalid. Note I don't mean for the movie specifically, but in general, you were expecting a superhero action movie, which Watchman actual isn't really at all. It's a superhero deconstruction movie.
Maybe you should rent 2001 next time... (actually just joking on that one, if you thought Watchmen dragged then I worry I'd be responsible for you self harming yourself watching 2001).
Try to be reasonable... its easier than you think...
