No. This misconception comes from confusing Mormons with the Amish, FLDS, or other religious groups. We don’t look down on those who do dress differently, as we believe that all men and women are free to “worship, how, where, or what they may” (Article of Faith #11). Chances are that you have seen thousands of Mormons, and you didn’t know it because they dress much like everyone else.
The Church of Jesus Christ does emphasize that its members should dress modestly.