Clem 55 and nanna-up-north said it well.
Ask them how they chose the pattern, what made them choose the fabric, how long have they been quilting, did they enjoy making the quilt, what would they do differently, what is their next project...
Go away making them feel better and with a smile on their face.
No need to burst their bubble. They will remember negative comments, half-hearted comments, and facial expressions far longer than necessary. Make this world a better place.