"I don't get people."
Who's not said something like that? In these instances, "people" usually means someone specific who either for an isolated moment in time, or long-term represents a subset of the population in general.
A lot of people don't "get people." I suppose it's just a reflection of how different we each can be; how vague the rules can be that govern human interactions and relationships. I also find it fascinating how those interactions are now being translated from the IRL world to the online world of social media. It's seems there are similarities between the "people" I don't "get" online and IRL (maybe another blog subject).