AT, calendar and plan builder were all major changes to TrainerRoad and had appropraitely big fanfare along with them.
Just release importing on runs and/or swims with minimal announcement and brand it as part of ongoing continuous improvement of the calendar. As others have said, this is the bare minimum that could be done. Matching to planned workouts (either automatically or manually) would be the next step in my eyes.
Someone earlier said it best, don’t let perfect be the enemy of the good.