OP, you raise many excellent points. I feel they are addressed by the fact that (apparently) we will be able to upgrade our exotics in TTK. To me, that's the perfect balance. We can keep iconic guns we love, but the new weapons will still be meaningful because we have to get new legendaries. Here is a perfect example of why that's good: Look at the rewards for PoE. They were universally panned by players, and most players have said they only cared about killing Skolas once, because after that, why bother when the rewards were useless compared to their raid legendaries? THAT is why it's important for the new gear to be more desirable than the old gear. All of your points about weapons in Destiny being more than stat sticks is true, which is why we get to upgrade exotics. But leaving ALL weapons upgradeable would leave only two outcomes: either the new gear isn't as good so no one cares about the content, OR the new gear is so much better that there is insane power creep.