unfestive
/ʌnˈfɛstɪv/Definitions
1. adjective
lacking the usual festive or celebratory atmosphere, quality, or spirit
“The unfestive atmosphere of the hospital made it difficult for the family to celebrate the newborn’s arrival.”
2. adverb
in a way that lacks festivity
“The couple decorated their home unfestively, choosing to keep things simple for their intimate gathering.”