If you need to hide feature work behind a flag on prod you're probably doing it wrong. There are a few times when you need to, but features can in most cases be written in a way that they can live inside production before complete. And learning to work like that also has the benefit of aggressively fighting features that drag on forever.

There are definitely exceptions, but 9 times out of 10 learning to develop features in a way that they can be continuously integrated to production will dramatically reduce features dragging on, decrease bug heavy feature launches and increase velocity.

EDIT: The downvoting system on HN optimizes for older, over the hill developers as is shown here once again.