“I'm so out of touch with pop culture these days.”
You're talking to a coworker and she mentions a popular TV show. You don't watch TV, so you've never heard of it. In fact, you don't know much about new TV shows, music, movies or politics, so you tell her this.
I'm so out of touch with pop culture these days.
"These days" means "recently". But "recently" is used to talk about things that have happened over the last few weeks or months. "These days" is a longer time period, usually from the last 6 months to the last 20-30 years. You use "these days" to talk about major changes in your life or in society.
I don't watch much TV these days.
Kids these days don't even remember what life was like before mobile phones and the Internet.
To be "out of touch with" a group of people means that you aren't paying attention to them and you don't understand them. But you wouldn't use this phrase to talk about a group of people from far away that you have never learned anything about. You use "out of touch" to describe not knowing a group of people that you're supposed to know well, or that you used to know well.
For example, you can be "out of touch with" teenagers or young people:
I'm not even 25 yet, but feel like I'm already out of touch with teenagers these days.
In addition to being "out of touch with" groups of people, you can also be "out of touch with" the ideas or culture that are associated with them. For example:
They accused Obama of being out of touch with the issues that ordinary citizens really care about.
"Pop culture" is a phrase that refers to all of the entertainment and news that most people in a society know about. Pop culture includes information about celebrities' lives, ideas from popular books, familiarity with songs on the radio, and so on. "Pop culture" can be used as a noun:
His films have had a huge influence on not only the movie industry, but on pop culture as a whole.
Or it can be used as an adjective:
He was a pop culture icon of the late '70s.