Fortunately, this issue was quickly resolved. A subsequent update to MX Player brought . This update essentially "unlocked" the app for KitKat users. Knowing this history assures you that while modern updates are not supported, a specific stable branch of MX Player works perfectly on your legacy hardware.
Since you cannot download the modern version from the Play Store, you will need to download a dedicated APK file from a trusted source. The ideal versions for KitKat are those released around late 2013 through 2014, specifically versions , as these were the builds that introduced official 4.4.2 support.
The current version of MX Player on the Google Play Store is designed for modern Android versions (Android 10+). Attempting to install it on KitKat 4.4.2 will result in a or an immediate crash.