I disagree, fatebringer is arguably one of the better weapons in the game, I see very little reason not to use it. Which is why destiny won't allow you to upgrade it, bungie wants us to crave the newer weapons so that we continue to play. If we used fatebringer till the end of destiny 3 then why would we keep playing. But If fatebringer could no longer kill enemies at level 40+ then why would anyone use it? Meaning that people would have to use new weapons, meaning more playtime to acquire.