a bit crap
When something is so bad, it's like it was made by someone who's never had a good day in their life.
'That cake is a bit crap. It tastes like regret.'
'Your singing is a bit crap. It's like a goat was trying to scream in a blender.'
'That idea is a bit crap. I think it was stolen from a kid who fell asleep during math class.'