(as) exciting as watching paint dry
Very dull or boring. Everyone loves that period drama, but, to me, it's as exciting as watching paint dry. Rachel fell asleep during the big game because she thinks that watching sports is exciting as watching paint dry.
*exciting as watching (the) paint dry
very, very dull. (Sarcastic. *Also: about as ~; as ~.) This book is about as exciting as watching paint dry. Listening to you is exciting as watching the paint dry.