Casual Shinji said:
Well, the plot is "stop the Collectors", and they stop the Collectors. Nothing much else that has anything to do with the overarching plot of stopping the Reapers gets touched upon at all. Mass Effect 2 was all about the characters. And it was mostly great in that regard, but the plot got totally shafted in the process
Yeah the game did focus a lot of it's writing on the characters, but that doesn't mean it had nothing to do with the overarching plot. The Collectors kill Shepard and start ransacking human colonies. Shepard comes back and wants to save the humans being captured. We learn that the Collectors are working for the Reapers (you know, those guys from the first game). We learn the Collectors use to be Protheans. At the end of the game we learn how Reapers are made, thus getting a better understanding of the enemy.
There were also plot hints in Tali's recruitment about the dark energy but that went nowhere...
Same with why Humans were of interest...
But yes, there was a plot in ME2 that unfortunately for you it seems was overshadowed by the heavy focus on character development (there was some, not lots) and missions mainly being recruitment/trust focused.