Why the surface raider is not obsolete

Has the surface raider become obsolete?

No; even a raider that is eventually found can disrupt trade and pull substantial enemy resources away from other tasks.

Modern surveillance does not make the surface raider obsolete simply because it can eventually locate the ship. Even lightly equipped pirates in small craft have disrupted merchant traffic, while a prepared warship could impose a much larger threat. The defender cannot ignore that threat and must assign ships, aircraft, intelligence, and time to the hunt. Those resources are then unavailable for other missions, making diversion and uncertainty part of the raider's value.