Apple TV A1469 compatible with Disney+

You cannot install apps on ATV3 but you can cast to an ATV# using Screen Mirroring on another Mac device. We did that this weekend, casting a Disney program from the Disney+ app on Dear Wife's iPad 7 to our Apple TV3 connected to our Sony 65". Worked great.

How to AirPlay video and mirror your device's screen - Apple Support

Maybe time to upgrade to an Apple TV 4K or HD model so you can add the apps you want to watch without having to Airplay.