That feature says "you remember the general layout" and not "you
remember the exact layout". So this does not necessarily mean that you suddenly
auto-succeed and can't ever get lost.
The feature is worded in a general enough way, avoiding exact mechanical terms. This seems to indicate that this feature depends greatly on the DM's own personal interpretation, allowing him to on-the-fly decide how powerful he really wants that feature to be.
You basically can't have a "one true answer" here, because the wording itself strongly invites a DM's ruling based on his preferences.
If you are a player, your best bet is to simply briefly talk to your DM outside of the game and ask him to give you a couple examples where that feature actually could make a difference in the game and by how much, just to get a better "feeling and understanding" of that feature.
If you are a DM, just use whatever mechanics that give you a "Wanderer feature power level" that you feel comfortable with. Just make sure the feature can have a real positive impact in the game, every now and then, so that the player will not feel that he has a mostly useless or valueless feature. Finally, it is also useful to read all the other Background features to get a better ideas of how much power/value/utility they can have.
If you want to focus on the epic battles, and not the gritty details, making navigating the wilderness, avoiding becoming lost, and finding food and water for the party, all be automatic successes, that is quite fine. After all, at higher levels the spellcasters have spells like Create food and Water and Teleport, which completely bypass the Wanderer feature. So letting the outlander shine before that happens is ok.
Another way too boost the usefulness of that feature especially in campaigns with not a lot of wilderness travel is to not limit it's utility to wilderness areas. Even in a big city, the Outlander would know the "layout of the settlement", etc..
Simply making the party require a bit less days of traveling and save a few gp on rations, is quite anti-climatic. Allow the party with an outlander to, once in a while, arrive at the dungeon well before the "time limit", letting them have way more rests than normal (making that adventure much easier), and making sure that the fact that they can "take their time" doing the adventure is entirely due to the competence of the Outlander.