We already knew relatively few people actually liked the design overhaul Snap (NYSE: SNAP) CEO Evan Spiegel foisted on Snapchat -- the changes caused user growth to slow and engagement with publishers to plummet -- but recent data from YouGov indicates things are only going to get worse.According to the YouGov BrandIndex, a daily online survey that tracks consumer sentiment toward brands, user sentiment with Snap among its key 18- to 34-year-old demographic plunged 73% following the redesign, essentially wiping out all the gains it had carefully crafted over the last two years.Snapchat users 18-34 years old really don't like the app's redesign.