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.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.