The phrase "piece of sh!t" for better or worse, is now so widespread its almost never meant literally. People who take it to heart shouldn't be working in _any_ client facing role.

It might be chinese culture to avoid criticize things directly, but it's also part of the chinese culture to give backhanded compliments like "5 out of 5 stars, when it works, which is never." I don't think the 笑里藏刀 (literally translated as "dagger hidden in the smile") aspect of chinese culture claims any moral high ground over the western straight shooting f* you.

I'm chinese too.