Humans have always been up for seizing neighbouring humans stuff and trying to rule over them and human nature hasn't really changed but the economics have. In the days of the British Empire it was far ahead industrially so could go stick railways in Africa and India and trade and it was kind of win win, sorta. Now everyone is more similarly developed and if you try it on in places like Ukraine they fight back at a similar tech level to Russia which ends up with ownership of some bombed out rubble in Ukraine and their own stuff burning.
For clarity I'm talking proper empire where you send in troops and install a viceroy, not just trading with places which is mostly what China does. The Taiwan thing is a special case of the communist party trying to take the remaining bit of China which has held out for a century.