not think much of (someone or something)
To have very little esteem or regard for someone or something; to have a negative opinion of someone or something. I can't tell my parents didn't think much of Mary's new boyfriend. The boss hasn't thought much of your work so far, so you'd better start trying a bit harder!
not think much of
Have little regard for, have a low opinion of, as in Bill doesn't think much of the carpentry work in that house. The phrase not much has been used in this sense since the mid-1800s.