If you are on your first relic for AK, you don't have the best gear. You aren't farming HM primals, Castrum isn't farmable like it was and AK is a road block. Your options are limited aside from farming WP like crazy. Though many HC players would say to farm WP, this simply isn't fun. If a game isn't fun, people don't play. "Nerfing" AK makes it so newer players can have opportunities without having to mindlessly grind. It's encouraging people to take on the challenges that come later.

For FATES, the truth is that people don't do them as much. Certainly some FATES are still farmed but many are not. This makes some FATES to hard because of less people. This isn't nerfing FATES, it's balancing them so people can do them.

For Sirius, people just don't do this dungeon. I get why. It's more difficult than other dungeons with no payoff. There is no incentive. Scaling it back isn't nerfing so much as it is balancing it and making it a more viable option to play alongside HM dungeons.