Most critics do not think much of his latest painting.

not think much of 是一个固定短语，意思是"对…评价不高"或"不太喜欢"，用来表达对某人或某事物不认可、觉得质量不好的判断。后面接 sb 指人，接 sth 指事物，常见搭配如 not think much of sb's work / of the new proposal。