Very niche, but my least favorite web re-design was the used camera retailer KEH.com (this was probably at least a decade ago). They went from a craigslist style listing (text dense, easy to drill down to any level from one page: Nikon Manual Focus ->Fixed length lenses->Nikon Brand || other brand. I think it was one or two clicks to get to a list of stock for a given category) to a regular e-commerce style page. Takes much longer to get to a nice looking page with less info and products displayed.
FWIW I haven't bought any gear from them since that happened, and they used to be my first stop for used equipment.
I think when you are selling to a buyer that knows what they want, its best to stick to a simpler information dense interface (Digikey, McMaster-Carr, etc.). I think a lot of websites try to "chase the trend" and look like Amazon, or whatever, without realizing that it is much harder to get that right than it is to get an ugly page right.