My favorite Saturday Night Live sketch is "The Danish Repertory Theater Presents: I Did It In My Style," an advert for a musical based on the life of Frank Sinatra made by people who had no idea what Frank Sinatra was and didn't have the budget or means to do anything about it, yet perplexingly made a musical about him anyway.
If you try to imagine MacGruber as The Danish Repertory Theater's version of a 1980s action movie - "we've seen the opening credits of one episode of MacGyver, so let's make a Cannon Picture!" - it's almost funny, but given that all the best lines have been given to the feller from laff riots like Breach and Anti-Trust, the movie appears to be working very hard to stop you from laughing. Everyone can succeed at something!
The very basic problem is that the action-comedy movie MacGruber simply is not as intentionally funny or exciting as the intentional action scenes and unintentional comedy of any given episode of MacGyver (though that's not really an apt comparison, as the picture works harder to satirize movies like Rambo and the work of Chuck Norris, but it all evens out because it's not as funny or exciting as those either); and in assuming that people will only laugh at something if it is intended as a joke, the makers of MacGruber have gravely underestimated their audience, who demonstrated their post-structuralist independence from the antiquated notion of authorial intention by seeing every other movie on release instead of MacGruber. People are smarter than you think. Particularly if you're an idiot.