1. Don't Over-Promise and Under-Deliver
2. Progress Gated by Random Outcomes is a Bad Idea
3. Temporary Content Needs to Have a Reason to be Temporary
4. Don't Imitate Systems Without Including the Core Functionality Players Expect
Destiny isn't a game that fails in every respect. It has superb shooting mechanics, with great feeling moment-to-moment action. It also looks beautiful and consistently runs smoothly, and the action is complemented by a beautiful score. The game oozes craftsmanship out of nearly every pore, but it fails to impress due to its crippling design weaknesses.
In the end, it goes to show that even a perfectly polished game can fail if its core design philosophies are misplaced.