Long copy works, because people want as much benefit-oriented information as they personally need to make the purchase.
Some won’t read much of it before buying. Others will read every word.
The key is to make the presentation of this information — your copy and the visual elements of the page — context appropriate. It needs to look and feel like your audience expects content from you to look and feel…
If you try to throw garish colors, exclamation points, and yellow highlighter at your audience when that’s not what they expect to see, you lose. In more ways than one.