take the gilt off the gingerbread
US /teɪk ðə ɡɪlt ɔf ðə ˈdʒɪndʒərˌbrɛd/
UK /teɪk ðə ɡɪlt ɔf ðə ˈdʒɪndʒərˌbrɛd/

1.
to make something less attractive or enjoyable; to spoil something that was initially appealing
:
•
The high cost of living really takes the gilt off the gingerbread of moving to a big city.
•
Finding out about the hidden fees really took the gilt off the gingerbread of the vacation package.