Normally, dictionaries translate "criticize" and "criticism" as "批评". In Chinese, 批评 has a very negative meaning, right?
Yes, it is a very negative and strong word.
Is there a Chinese term to describe "positive feedback"?
Yes, we have 善意的批评 for positive criticism and 正面的反馈 for "positive feedback".
I found the term "好评"; is that used?
Yes, 好评 is commonly used, but it is not exactly the opposite of criticism. you can 批评 someone, but you can't 好评 someone, 好评 is only referring to something you have done. it is kind of "acclaimed"
His work was critically acclaimed. 他的工作得到好评
His performance won him much praise. 他的表现赢得了很多好评。