hear about
Something is only talked about if talking about it accomplishes something. Gen X doesn't raise any strong feelings with anyone, so they're not talked about. They're still there obviously.
The reason why is complex, and I'm no expert myself. However, from what I gathered about recent history, what seems most likely to me is that the time gen x'ers grew up in was very stable in the sense that economy was good, no major wars were happening, the cold war was "ending". So the only thing gen x'ers had to worry about was themselves. So they did. And you don't really need to talk about someone that just keeps to themself. They cause you no issues.
Another theory of mine is very simple: humanity changes over time. The larger the time, the larger the change. Differences between humans breeds conflict as their interests collide. Since boomers are the current oldest larger impactful generation, and gen z are the youngest, the difference between them are greatest. Thus the conflict between them is highest, thus there are a lot of people talking about those problems. I've been hearing less about millennials as well.