Thus, you cannot install the latest .apk from the Play Store or even a 2025 version. You need a from the 2019–2020 period.
Enjoy your KitKat device while it lasts. It is a museum piece that still texts—for now. Whatsapp For Kitkat 4.4 2 Download Old Version
Check if your device has a "Custom ROM" (like LineageOS) available that can bring it to Android 5.0 or higher. Thus, you cannot install the latest