The design choices. For instance: Every boss is now in a 6x6 room with little to no cover. They also get to be invincible in stages while you bounce around the room trying to avoid adds. Part of the fun in d1 strikes was learning the terrain. Finding safe zones for specific times. Learning a routine over time to help you do it faster. The new bosses are simply bullet sponges with intermintant invonarability in a room full of adds and no cover. The only strategy now consists of sporadic jump/dodge/shoot. =not very fun.