Games and apps like Snapchat can go that route, making the user learn a completely different UI. But for practically every other app type, going with a new UI and discarding the platform defaults for navigation, buttons, etc. is only going to hurt you in the long run, both from a user perspective (no one has the patience to learn a new UI with every app), and from a effort standpoiont (it takes way longer to develop your own UI than it does sticking with platform defaults).
That has been my experience at least, every time we changed something from "our" way to a more default platform way, we've seen better metrics and retention across the board. We even try to avoid platform specific things like swipe to delete etc., because the general user does not use those features, even if you "teach" them in the onboarding.
This doesn't mean that you shouldn't style your app etc to give it an identity, and there's actually a lot of room you have even when sticking to default elements.
That has been my experience at least, every time we changed something from "our" way to a more default platform way, we've seen better metrics and retention across the board. We even try to avoid platform specific things like swipe to delete etc., because the general user does not use those features, even if you "teach" them in the onboarding.
This doesn't mean that you shouldn't style your app etc to give it an identity, and there's actually a lot of room you have even when sticking to default elements.