I don't see why it would take years to learn to write an app in Swift or Kotlin (or React Native or Flutter), even starting from zero. I'm not trying to be cute here.

There are probably 50 high quality end to end tutorial for building a video streaming app. I guess using Firebase is tying you in to a service, but so what? If it's for 4 friends it doesn't have to be infinitely scalable. Just by writing an iOS app you're tied to Apple, right? And surely an app isnt a failure just because it has dependencies?