Since Spellcasting and Circle Spells are class feature (which you retain), I don't see why you shouldn't use your usual spell save DC while being a Moon Druid in Wild Shape. If you were supposed to recalculate your spell save DC by using the Proficiency Bonus of the Beast, it would say so but I can't see any reason it should be RAW (and definitely not RAI).
Thor
2023-12-15 06:50:54 +0000 UTC
What if all Druids can wildshape using stat blocks - but the moon Druid can also use powerful templates when using wild shape? (If you come up with a better idea please post it)