Don't be. Diesel electric subs on batteries are notoriously hard to track because there is almost nothing putting out noise, the only way to passively track submarines. AIP subs are just as hard to track for the same reason, and add to that their underwater endurance is counted in weeks and not days. The sub that's quieter is the sub that wins, nuclear or not.
Now bear in mind this a technologically advanced sub from a highly industrialized country manned by a skilled, professional crew. And I cannot emphasize the quality of the crew enough, the best sub in the world is worthless if you put a bunch of amatures onboard it. Having Gotland on hand is an excellent idea for training, because if you can beat them then you have truly beaten the best at the business with the platform you're training against.
I understand that acoustics are still the primary means of detection. But, don't we also now detect magnetically...and via ultra-low frequency acoustics (subsonic physical disturbance)?