I wish this was true. I am locked-in with Firebase and would love to self-host now that I have resources. Sadly I will have to rewrite the API.
It's not that Firebase is not great, I just want to take control back.
To be fair, I think Horizon is one of the more promising Firebase alternatives. However, it has completely different semantics, and is quite immature at this point (look at the limitations: http://horizon.io/docs/limitations/). But if Firebase remains proprietary and Horizon continues to improve I could certainly imagine that rewriting my app will eventually start to look attractive.