The ZTE Spro 2 runs on Android 5.1.1 Lollipop. Modern apps (Netflix, Disney+, YouTube) have minimum API requirements (Android 6.0+). Even with the latest firmware, you cannot install the newest versions of these apps.
Disclaimer: I am not affiliated with ZTE. Flashing incorrect firmware can permanently damage your device. This guide is for informational purposes only. Proceed at your own risk. zte spro 2 firmware download