Inexpertness

It may be too difficult for the trainee - small dog, tall weeds!

He can't paint for toffee!

只会一招的小马, 仅擅长一件事的人

He's a one-trick pony when it comes to cooking, but his spaghetti is legendary.

在烹饪方面他是个一招鲜，但他的意大利面是传奇的。

I used to be a great piano player, but I'm out of practice now.

He's a talented musician, but he's still wet behind the ears when it comes to performing on stage.

When it comes to modern technology, my grandparents don't know the meaning of the word.

He didn't have any data to back up his claim; it was just a finger in the air.

John is a real jack of all trades; he can fix the plumbing, repair the roof, and even bake delicious cakes.