When I mentioned the engine it wasn't about the graphics it's about the coding issues it has and it's why they're a lot of issues in this game that Bungie will never get to because of how long it can take at time to preduse the content before that can look over what they need to adjust. You should look it up, I watched a video and it talks about how the devs would basically do what they wanted and not communicating with one another over the years that caused other issues. So the drip-feed part is self-explanatory.