Ask HN: Why are some websites so bad at describing their product? 6 years ago
The best resource I have seen that discusses this issue and offers a solution is https://www.mystorybrand.com/
Potential customers should be able to answer these questions within 5 SECONDS of reading the site, or marketing material: 1. What do you offer? 2. How will it make my life better? 3. What do I need to do to buy it?
You can do this with fewer than 300 words on your sales page.