No idea yet when Luke goes off the grid, but in Aftermath there’s talk of Mon Mothma wanting to demilitarize the New Republic, and at the end of Lost Stars the Imperial Remnant withdraws to the Unknown Regions to regroup and rebuild. Both of those are set decades before The Force Awakens, but they point towards the Resistance being a proxy force and the First Order not yet being well established like a lot of folks here have conjectured. The movie could have done a better job of explaining it, but the nuEU has set it up reasonably well.