Honestly I think the ability to craft weapons has probably had an impact on player count. If players were still grinding for a good Luna for example, but with the addition of crafting there's less need to grind endlessly. But that just highlights that there isn't really enough to do in game. So much of the content is irrelevant unless it's on rotation or can really only be played once per week. When you're close to the power cap and don't have any weapon or armor rolls you really need, what's the point in playing daily? Essentially, Bungie broke their own long term gameplay loop with craftable weapons.