Quite the opposite in fact, it’s to guarantee the maintenance of applications we already enjoyed and to steer their development in a direction that benefits multiple desktop environments. The goal of the X-Apps is not to reinvent the wheel.
For instance, Totem 3.18 was radically different than Totem 3.10 which shipped with Linux Mint 17, but Xplayer 1.0 (which was the default media player in Linux Mint 18) was exactly the same. Within Linux Mint, users didn’t need to adapt to X-Apps, because in many cases, they were very similar or exactly the same as the applications people were already using. To be backward-compatible (in order to work on as many distributions as possible).To provide the functionality users already enjoy (or enjoyed in the past for distributions which already lost some functionality).To work everywhere (to be generic, desktop-agnostic and distro-agnostic).To use traditional user interfaces (titlebars, menubars).