I think a lot of people don't consider the words they learn and what places they fit into. I'm a young person that grew up with social media very heavily embedded in my life. Throughout school, if I knew something was slang, I would think of it as such and only use it with friends. If I was talking to a stranger, a teacher, parents, etc. I would not use those words as I didn't know if they would be familiar or understand. But I see many people don't do this, they assume everyone has their same level of knowledge. I don't know if theres a better term but I think of it similar to code-switching. You need to know your environment and who you are interacting with to act appropriately. There is nothing inherently bad with using modern slang, but it needs to be thought of as such.
Having now graduated some time ago, my main communications in real life are at work with customers or with coworkers much older than myself. And when online unless im in a specific group I try to keep a baseline of normalcy when chatting.
Forgive me if this sounds like the ramblings of a half asleep person, as that is what they are.