Observing hindrances & seeing impermanence vs right effort

I'm not sure whether it has been poorly taught by a monk but as far as I know the Buddha never really taught to just merely watch the hindrances, right? The sixth factor of the N8P is right effort and it calls us to do something about the hindrances. But why then does the Buddha at other times say that we have to see the impermanence, the unstability (non self) and the unsatisfactory nature of thoughts, feelings, emotions etc? Should we do both approaches or mainly right effort?