My experience has been that "chosen family" is a thing that works when you're young, but almost always falls apart when you get older. This has happened to countless people I know. Life throws all kinds of curveballs, incentives change, conflicts arise, sometimes very intense conflicts. Empirically, chosen family is a structure that works in a particular place and time, then disintegrates when conditions change. Real family isn't like that; there is a very strong anthropological connection wired into us that doesn't go away when the situation changes.

Of course it's different for everyone, some families are so tragic they may not be worth preserving, etc. But that's an outlier-- the modal experience is that the power of family is precisely in the fact that you don't get to choose it.