non linear level design

I feel a big problem with a lot of the newer games released is that the direction you need to go is always right in front of you. I miss being able to get lost in a level and exploring for a little bit, this doesn't mean that the player should have no idea where he is going, just that the next waypoint should be somewhere other than forward. Backtracking in a level is not always bad, especially if the areas change their behavior. if an asteroid field was easy for the first part of a mission because the player was fighting slow ships with no escorts, it could change to be one of the hardest areas after the player is faced with a swarm of small agile ships