The popularisation of the concept of Central Europe stems from some people being ashamed of being from Eastern Europe and feeling inferior to Western Europe. Eastern Europe is defined by the Iron Curtain whose effects are still visible today, while Central Europe is a category created purely by selecting a region on the map without regard for political or cultural factors, just to push Eastern Europe further East and exclude some countries from it. It’s fairly arbitrary. I don’t see Eastern Europe as inferior and am not ashamed of being from a part of it, so I see no point in using an arbitrary term like Central Europe.

Mitteleuropa is an old concept, much older than the Iron Curtain. For example, the old boundaries of the Austro-Hungarian empire catch quite a lot of it. I've been told that places like Slovenia are pretty different from places like Serbia, and similarly for western vs. eastern Ukraine.

In the case of Poland though only a tiny fraction of it was captured by the Austro-Hungarian Empire. The largest portion was captured by Russia. Second largest by German Empire. I have great-grandparents from each of those.

Moreover prior to the fall of the Iron Curtain the term Central Europe wasn’t used much. After that though some people like Milan Kundera started popularising it much more out of sense of inferiority.