The creatives behind these mods have sought to fix the Minecraft bosses by adding their own. That said, Minecraft has one of the biggest modding scenes in all of gaming, with some incredibly talented people out there making excellent new additions to the game. Those looking for a series of intricate and challenging boss fights will much prefer Terraria's RPG experience. The Warden looks to be something better in this regard as a creature that players aren't supposed to be able to kill, but that's just one creature.
The Ender Dragon isn't a difficult boss, and The Wither can be a challenge but is easily beaten when prepared for. In a game with infinite possibilities, Minecraft's lack of menacing challenges for the player to overcome can be rather disappointing for some.
