That its a monkey's paw once again. Players asked for a repeatable grindable source of bright dust, Bungie "gives" it to the players but the finger curling is that now seasonal challenges are gone and you are more fomoed on getting bright dust. They keep doing this to the community then wonder why the playerbase hates their guts and is so toxic towards them and its because almost every change they make has some twisted downside every time. The only reason that unstable cores are getting completely removed is because they are desperate, and they were originally planning to "rework" the currency before announcing they are just removing it. Power levels are the same deal and I almost guarantee they are trying to figure out a way to monkey's paw the community once again with power grind resetting or something.