Heroic dungeons don’t give anything worth anything. They used to give a daily bundle of Legendary tokens, which made them rewarding, and feeling stupid OP once a day was fun.
You used to be able to mix & match sets from various raid difficulties. Now that ilvl is the only thing in existence, lower difficulty raids are pointless.
Artifact power used to level your weapon up along with you. Technically, this still vaguely exists with the necklace and mini-legendary-set bonus things, but man this new system is awful, at least they acknowledge that one bit and are overhauling it in 8.2
You also used to be able to get Legendaries from literally anything, so theoretically killing some random mob in the world could be worth your time & effort.
Exactly, not enough soft pretzels.